The bandwidth is 173.78 GHz and the insertion loss is only 0.0338 dB.In this paper, we propose a polarization-independent optoelectronic modulator based on the electrical absorption effect of graphene. Firstly, we use the simulation software COMSOL Multiphysics to design the structure, and find via changing the applied voltage on both ends of the graphene that the equivalent refractive index of graphene can be changed, thus changing the light absorption capacity of the modulator. The waveguides in the transverse magnetic (TM) and transverse electric (TE) modes have almost the same extinction coefficient by making a double-layer graphene ridge structure in the center of the silicon-based waveguide, which can achieve approaching modulation depth in the TM and TE modes. At 1550 nm wavelength, the two-dimensional cross-section of the structure is analyzed by the FEM method using COMSOL Multiphysics to obtain the effective refractive index of the structure. The simulation results show that when the distance between the double-layer graphene isolation layer is  Two layers of graphene are attached to each gold electrode, which increases the graphene’s interaction with light and prevents free electrons from infiltrating the silicon layer. The modulation depth of the modulator reaches 0.16 dB/μm, but the 3 dB bandwidth does not increase, mainly because the RC time constant of the modulator remains unchanged. The modulator structure of this study provides the basis for our design. Kim et al. placed graphene in the area of the waveguide with the strongest light intensity and used an hBN spacer with a thickness of 7 nm to separate graphene layers and between graphene and silicon waveguide, enhancing graphene-light interaction and modulation depth [The modulator made of traditional photoelectric materials has been widely used in the field of optical communication ,2,3,4. I silicon ,6,7. Gra silicon , so it h silicon , which s silicon ,12. In 2 silicon  covered  silicon , and theon depth . Our groon depth .At present, most of the current graphene-based optoelectronic modulators are polarization-dependent ,19,20, wThis paper presents a polarization-independent optoelectronic modulator based on the graphene absorption effect and simulated by COMSOL Multiphysics software. By transferring the graphene to the upper surface of the ridge waveguide and depositing the silicon material of a certain thickness, the double-layer graphene is positioned at the center of the silicon waveguide, and the interaction between the graphene and the light field is enhanced. Because graphene can fully interact with the light field in both the horizontal and vertical directions, the TM and TE modes have the same extinction coefficient, achieving the purpose of polarization independence. The designed modulator in this paper provides a theoretical foundation for the further development of optical communicationThe structure of the polarization-independent optoelectronic modulator based on the graphene ridge structure proposed in this paper is shown in Double-layer graphene uses the hBN with stable chemical properties and high refractive index as the material of the isolation layer. By selecting the appropriate thickness of the isolation layer, both the high extinction ratio and the wide modulation bandwidth can be achieved. When the graphene is placed horizontally in the center of the silicon waveguide, the graphene mainly interacts with the TE mode light in the waveguide; when the graphene is placed vertically in the center of the silicon waveguide, the graphene mainly interacts with the TM mode light. Therefore, when the graphene has both horizontal and vertical coverage, the TM and TE mode light can be modulated at the same time. By choosing appropriate values for the length of the graphene in the horizontal and vertical directions, it is possible to achieve polarization-independent optoelectronic modulation.e is the elementary charge; μ and the chemical potential The graphene conductivity is the concentrated expression of its optoelectronic properties, which is defined by the Kubo equation .(1)σ(ω)grapheme . Figure Graphene is a two-dimensional material with zero band gap, which can respond in the wavelength range of visible to near-infrared light, thus escaping the “long wave limit” of traditional detectors. When the incident light energy is weak, the light absorption properties of graphene are mainly determined by the carrier concentration of graphene. That is because the graphene’s ability to absorb light depends on the Fermi level of the graphene. When the bias voltage is applied across the graphene, it causes the change in the carrier concentration and the Fermi level . This red; the distance between horizontal graphene and the bottom surface of the silicon waveguide is Based on the finite element method, the mode analysis module of COMSOL software is used to simulate the two-dimensional cross-section of the modulator in α of the effective refractive index in the TM and TE modes is almost equal. When At 1550 nm light wavelength, the real and imaginary parts of the effective refractive index with chemical potential can be obtained by using the COMSOL software. As shown in α of the effective refractive index with wavelength is shown in When the chemical potential is equal to 0.51 eV and the wavelength of the incident light is changed from 1400 nm to 1700 nm, the variation of the real part As shown in L is the effective length of the modulator; The extinction ratio is the important parameter of an optoelectronic modulator and the index to measure its switching performance. The expression of the ER of the modulator proposed in this paper is shown in Equation (6):L = 3 μm, changes the incident wavelength λ, and calculates the change of the ER value for both TM and TE modes with the incident light wavelength as shown in As shown in odulator . In summR is the equivalent resistance of the device, mainly including the resistance Rg of the graphene itself and the contact resistance Rc due to the contact between the metal electrode and graphene. Since the resistivity of the graphene is very small, the resistance Rg is negligible. Only the resistance Rc is considered in the calculation. Its value is generally The important parameter for measuring the modulation rate of an optical modulator is the modulation bandwidth The factors that determine the modulation bandwidth of graphene optical modulators are mainly the equivalent capacitance and equivalent resistance of the modulator ,34, as sC, mainly including the parallel plate capacitance CP formed by the intermediate isolation medium, and its calculation equation is as follows:S is the area of the plate capacitor, S = wL, w = 660 nm is the width of the active region, L = 3μm is the length of the active region, d is the thickness of the double-layer graphene insulation medium. When d is proportional to d is changed, the modulator’s extinction coefficient α will also change. α with the chemical potential in the TM and TE modes at different separation layer distances d. As shown in d is inversely proportional to the peak value of α. This also shows that the larger d, the smaller the ER of the modulator. Comprehensively, this paper chose d = 20 nm, and then obtained The equivalent capacitance of the device is 69.8 GHz .αmin is the minimum value of the imaginary part of the effective refractive index, which is taken as L = 3 μm is the effective length of the modulation, λ is the incident wavelength. After calculation, the insertion loss of the optoelectronic modulator is 0.0338 dB.The total optical power loss caused by adding the optical modulator to the optical transmission system is called the insertion loss of the modulator. These losses include the transmission loss and the coupling loss between the light source and the waveguide. This article only considers the effect of transmission loss on the modulator insertion loss. The definition of insertion loss is as follows:d = 20 nm, the TE and TM modes can achieve extinction ratios up to 110 dB over the wide communication band by selecting appropriate “ON” and “OFF” switching points. The bandwidth is 173.78 GHz and the insertion loss is only 0.0338 dB. The proposed modulator provides the important theoretical reference for the development of large-scale integration of optoelectronic communication devices.The paper presents a polarization-independent optical modulator based on the double-layer graphene ridge structure. The double-layer graphene ridge structure can interact with the light field in both vertical and horizontal directions. By changing the graphene chemical potential and operating wavelength, the COMSOL Multiphysics simulation software was used to study the effective refractive index of the modulator in TM and TE modes. Due to the electric field distribution of the TM and TE modes in the designed modulator being orthogonal, polarization-independent optoelectronic modulation can be achieved through the two parts of graphene. Placing the graphene ridge structure in the center of the waveguide enhances the interaction between the light and graphene. Under the premise of ensuring low polarization tolerance, the ER of the modulators in TM and TE modes are improved. The results show that: when the graphene chemical potential changes, the imaginary parts of the equivalent refractive index in TE and TM modes have almost equal values, and both reach the maximum value when


This review focuses on the comparison of different methods for hydrogen storage, mainly based on the carbon-based materials and focuses on efficiently using graphene and its different forms to serve a purpose in the future H2-based economy.The energetic and climate crises should pose a challenge for scientists in finding solutions in the field of renewable, green energy sources. Throughout more than two decades, the search for new opportunities in the energy industry made it possible to observe the potential use of hydrogen as an energy source. One of the greatest challenges faced by scientists for the sake of its use as an energy source is designing safe, usable, reliable, and effective forms of hydrogen storage. Moreover, the manner in which hydrogen is to be stored is closely dependent on the potential use of this source of green energy. In stationary use, the aim is to achieve high volumetric density of the container. However, from the point of view of mobile applications, an extremely important aspect is the storage of hydrogen, using lightweight tanks of relatively high density. That is why, a focus of scientists has been put on the use of carbon-based materials and graphene as a perspective solution in the field of H In our daily life, energy is one of the most integral and necessary elements for us to function. As a result, the constantly growing consumption of energy from various sources is an easy trigger for the emergence of an energy crisis in the area of the whole world. This crisis is related to both the oversupply and demand for energy in every area of life, as well as the constant use of fossil fuels for this purpose. This is mainly due to the constantly growing world population, as well as the growing demand for new technologies and rising living standards in the world. Also, most of the world’s economies are based primarily on the use of non-renewable energy sources ,2.It is estimated that up to 80% of the total energy used in the world is the energy obtained from mainly three sources: coal, natural gases, and petroleum. These sources are not inexhaustible, however, the energy crisis related to the use of these fuels may have its climax already in 2035 and last for several years. Limited sources of fossil fuels and rising oil prices, combined with the growing greenhouse gas emissions, pose a challenge to the search for new energy sources and the possibility of using it in many branches of the energy industry .Hence, by observing the trends in the growing needs of the energy industry, scientists are looking for alternatives to traditional energy sources with the benefit of sustainable methods as an alternative fuel source. On this basis, several years ago, work began to intensify on the use of hydrogen as a sustainable energy source ,6,7. On Hydrogen is an element of a great importance. As it is the simplest, the lightest, and the most abundant particle on earth, its accessibility makes it a perfect possible solution in terms of many industrial applications, including its use in energy industries. The use of this element has many advantages with very low number of disadvantages, and all these are mentioned in However, even if hydrogen can be produced via diverse methods, still the requirements on the possibilities of the most effective hydrogen storage has to be exploited. This review examines the possible ways for storing hydrogen as a potential energy source, highlighting the use of graphene-based solutions as a promising perspective in this field.One of the most difficult challenges for using hydrogen as an energy source is its storage. When designing possible solutions in this area, first of all, one should take into account both economic and purely technological aspects .Chemically, with the help of different liquid or solid chemical compound;Physically  and the extremely low density of hydrogen (0.09 kg/NA m³) in the gaseous and exceptionally high density (70.9 kg/NA m³) in the liquid phase. Additionally, the methods currently used are limited by other factors. First of all, the disadvantage of the methods used is the significant energy loss, which amounts to 40% in the case of condensation and up to 20% of the hydrogen content needed to compress the gas. Moreover, a very important issue is also the necessity to limit the use of high-pressure and cryogenic storage, mainly due to the social aspects that negatively associate the use of gas under pressure and difficulties with stopping the release of liquid H2 .In recent years, several phenomena and methods has been applied to fulfill the needs of stationary hydrogen storage. Among them, the most popular ones are listed in 2 absorption and desorption properties in storage materials, mainly due to the fact that its storage in liquid form is difficult because hydrogen condensation requires very low temperatures.A significant technological breakthrough is needed in order to make hydrogen storage efficient and the most economically effective alternative compared to compressed and liquid hydrogen. This means either its solid or liquid storage. However, there is an urgent need to improve the HTaking this into consideration, the most promising routes for hydrogen storage are solid materials, whose role will be to chemically bind or physically adsorb hydrogen at bulk densities greater than liquid hydrogen .The scheme in 2 as an energy source will be present in almost all areas of our everyday life [The literature review of the current state-of-the-art in terms of hydrogen use and the hydrogen storage technologies, points out that in not distant future, the use of Hday life .For now, industrial use of this gas is mostly focused on ammonia production, petroleum, and metals refining . Over th2 and O2 (originated from fuel cell) are releasing electrical and heat energy. Both these methods allow the engine to start working, but the problematic issue is not the way how this is supposed to work, but the demanded size for the hydrogen storage area.The need to find an optimized way for hydrogen storage, especially for mobile applications, has originated mostly from the issue of really low density of this gas which results in the need for inadequately large surface area of the fuel tank . In the Taking these into consideration, it can be clearly seen that storing hydrogen for the mobile purposes still poses a major research challenge for materials engineers. The main difficulties come from the need to achieve a storage medium that enable to store hydrogen with its great density, combined with fast, reversible kinetics of charging and discharging. To achieve this, the considered material requires strong chemical bonds and close atomic packaging. However, to provide a demanded kinetics of adsorption and desorption, requirements are focused on weakly bonded material structures, brittle at moderate temperatures. Moreover, to facilitate a rapid diffusion of hydrogen, loose atomic packaging of storage material and adequate thermal conductivity (in order to prevent heat induced degradation) are needed. By now, scientists seek a way to fulfill all these requirements. From several years, the novel ways developed to serve these purposes come from the field of nanosciences. The possible use of nanosized materials, especially with large surface area hybrid structure, allows the demanded multifunctional action of material serving as the hydrogen storage source .The main contraindication to using hydrogen as an energy source in mobile applications is still the low gravimetric density achieved by the available systems . Carbon2 hybridization. Material in such form has an obvious tendency to restack and agglomerate. In general, graphite can be treated as numerous layers of graphene that are arranged parallelly via van der Waals bonds that maintain the distance between the planes equal to 0.335 nm [Graphene belongs to two-dimensional materials, sometimes referred to as single layer materials. It is a class of nanomaterials merely one atom thick. These materials are extracted from layered materials with strong in-plane chemical bonds and weak coupling between the individual layers or artificially synthesized on the substrate. Experimentally, it was first developed via scotch tape peeling of graphite by Andre Geim and Konstantin Novoselov . In its 0.335 nm . The lay0.335 nm .Graphene, its properties, and available applications are highly dependent on the manufacturing method used to obtain it. Exfoliation is a process of separation of the layers of the material that can be conducted micromechanically (like during graphene discovery) or in liquid phase. Large-scale production of graphene using this method is rather problematic, which stays against its common use for hydrogen storage. In case of use of chemical vapor deposition (CVD), the manufacturing requires formation of graphene on the substrate due to segregation of carbon atoms dissolved in metals with high solubility of that element  or direc2 is not able to freely enter between individual planes, and as a result, adsorption occurs mainly at the outer planes [The hydrogen storage in carbon-based materials is based both on the physisorption and chemisorption. Physisorption usually occurs with hydrogen in the molecular form and behind its mechanism is the weak interactions with the surface like those based on van der Waals forces, electrostatic and dispersion interactions . The ther planes . For ther planes . From thOne of the important aspects of using carbon materials in terms of hydrogen storage is their large specific surface area , which hThe next sections are devoted to the description of various carbonaceous materials potential, starting from those not based on graphene structure, in hydrogen storage. In the part entitled “Graphene-assisted hydrogen storage” the readers will first get acquainted with solutions based on plane graphene and its decoration mostly with metals. The next step is related to the transition from 2D to 3D structures. That can be achieved either via integration of graphene with other materials to form composites or spatialization of graphene itself.60), allow to obtain up to 7.7 wt.% hydrogen [Fullerenes , and then high-temperature modification in an alkaline environment (most often KOH) with the participation of water vapor. The storage of hydrogen in active carbon is probably based solely on the principle of adsorption without the formation of a permanent atomic bond. As a result, the properties of the material under consideration strongly depend on its parameters, such as the size and morphology of the pores, and the specific surface area ,60. The 2/g and is inversely proportional to the size of the pores.Active carbon  obtained2/g. For the material obtained in this way, the gravimetric density of adsorbed hydrogen at 77 K and 40 bar pressure ranged from 0.9 to 7.01 wt.%.Similarly, the porous carbon obtained  in the pThe most effective method of modifying the structure of porous carbon is the proper selection of intermediates in such a way as to obtain the desired chemical composition or structure after the hydrocarbonization and activation process. In the work of Blackenship et al. , the celStorage of hydrogen in carbon materials such as nanotubes, fullerenes, or porous carbon, for the sake of automotive applications seems to still be a distant future. Conducted experimental researches still mainly result in low level of achieved gravimetric density. Moreover, there are still unwilling handling aspects to overcome such as: instability of those types of materials and their key parameters within the consecutive cycles of sorption/desorption, limitations related to the necessary usage of cryogenic temperatures or high pressures etc. Among the emerging solutions are those based on graphene.Basic material that takes part in sorption and desorption processes;Scaffolding for metal catalysts allowing the spill-over processes to take place ;Material used to modify the existing solutions, e.g., composites based on graphene and metal hydrides.For hydrogen storage applications, graphene can be used directly as:The key to achieving a satisfactory sorption capacity of graphene-based systems is the synergistic effect of hydrogen chemisorption and physi-adsorption. By cyclically treating HSMG graphene sheets ,62 with 2/g. The experimental work carried out at a pressure of 10 bar showed the sorption capacity of this form of graphene at the level of 0.1 wt.% at room temperatures and even 1.2 wt.% for cryogenic temperatures. Kostoglou et al. [2/g. Such graphene structure at cryogenic temperatures and a pressure of 1 bar was characterized by a sorption capacity of 0.66 wt.%.Literature reports indicate that graphene and “graphene” materials in their pure form are not able to exceed the hydrogen storage barrier of a few percent by weight see . To achiu et al.  exfoliat2 adsorption of 1.9 wt.% and 1.34 wt.%, respectively, for a pressure of 80 bar and room temperature. The difference was related to the presence of oxygen-containing functional groups that separated the graphene layers more.In the case of using multilayer graphene as a material for hydrogen storage, the obtained values of sorption capacity depend, inter alia, on the interlayer spacing. During oxidation, it is possible to control the distance between the graphene layers so that the hydrogen storage capacity is as high as possible. This effect can be observed when comparing the sorption capacity of GO and reduced-GO (rGO) by Rajuar et al. . At roomMany of the published studies in the field of possible use of graphene for hydrogen storage purposes include only calculations or preparation of simulations of possible structures based on this material. These analyses show, that depending on the decorator used, it is possible to achieve not only 5 wt.% when using calcium as a catalyst  but evenThe main assumption behind the use of transition metal decorators deposited on graphene structures is related to the so-called “spill-over effect.” This process involves the initial dissociation of hydrogen in molecular form due to the presence of a catalyst dispersed on the surface. Then, migration of hydrogen to adjacent fragments of carbon material is possible, terminated by the diffusion of atomic hydrogen on the carbon support ,83. ThesThe mechanism of spill-over processes is a subject of ongoing scientific discussions. There are still voices that its influence on hydrogen storage is exaggerated and the process itself may not take place at all . These vThe spill-over effect was confirmed, among many others, by research conducted on the use of platinum as a catalyst. Zhou et al.  in his rOne of the significant problems in decorating graphene    [3 to the aqueous GO suspension, followed by drying and thermal reduction processes. The obtained results were significantly higher than in the case of mechanical mixing of TiO2 nanoparticles with graphene, probably due to obtaining a better dispersion of the decorator [2 storage from 1.36 to 1.26 wt.% for GO/V2O5 and GO/TiO2, respectively.Research conducted on graphene decorated with various concentrations of titanium dioxide   showed tecorator . Hong etecorator  applied The presence of defects and strictly defined amounts of functional groups  also affect the spill-over effect, e.g., by reducing the hydrogen migration energy barriers, which has been confirmed for various carbon materials ,98 and i2 molecules for each scandium atom in their calculations. Moreover, Kim et al. which worked with the same decorator but doping graphene with boron and obtained about 7.0 wt.% [Luo et al.  have pro7.0 wt.% .Research conducted on the doping of B-doped graphene by Faye et al.  also con2 storage, you can find those that are also green at the stage of planning the experiment. Vinayan et al. [The purpose of research on hydrogen storage in graphene structures is undoubtedly the broadly understood good of our planet’s humanity and ecology. Interestingly, among the proposed approaches to use graphene for Hn et al.  proposedNevertheless, these are still simulation values that are unlikely to be obtained in tests. On the other hand, many hopes are attached to various forms of graphene oxide and its reduced form. Moreover, the oxide can be decorated with nanoparticles, just like graphene. The experimental results currently indicate hydrogen adsorption in such structures reaching 5 wt.% ,115,116.The graphical representation of the undertaken approaches of graphene-decoration for the sake of hydrogen storage is presented in 4 composite with porous fluorinated graphene structures with a specific surface area of about 220 m2/g. As a result of applying 20 wt.% multi-layers sheet-like structures, many important parameters in terms of target hydrogen storage applications have improved. The desorption temperature was lowered by about 120 °C in relation to the unmodified hydride, as well as the kinetics of hydrogen desorption was improved . The developed material achieved a sorption capacity of 3.45 wt.% at 400 °C, which is 2.57 times more than that of unmodified LiBH4. The changes resulting from the use of the LiBH4 composite and the fluorinated graphene were related to easier recombination of hydrogen molecules on the surface of the material resulting from more reactive sites.Zhang et al.  in their2 + NH4Cl/graphene composite was proposed by Luo et al. [4Cl over MgH2. However, the presence of graphene had a positive effect on the purity of the recovered graphene, which was as high as 97.26%. The sorption capacity of the composites was 8.29 wt.% and 7.23 wt.% for the 5% and 10% graphene content, respectively.MgHo et al.  to reducAnother interesting example of a composite with the potential for hydrogen storage is the combination of magnesium with graphene nanoplatelets (GNPs), i.e., structures containing up to 100 graphene layers . By chan−3 S/cm and in that form can act as supercapacitor electrodes.Numerous approaches have been undertaken to move from the plane graphene to its spatial forms: foams or sponges, various scaffolds, pillared graphene, or 3D prints. Even hydrothermal methods can be introduced to achieve spatial forms of graphene . A high-3 solution. For the 3D graphene, the polymer layer was removed with hot acetone. Depending on the type and supportive metal foam the graphene foam with surface area up to 850 m2/g and porosity of even 99.7% was achieved.In case of spatial graphene manufactured on scaffolds or templates acting as a support, very complex structures can be achieved by means of e.g., chemical vapor deposition or infiltration process in a liquid medium. Chen et. al.  produced2/g. The contamination of the final product with residues of scaffold is a problematic case of methods based on various templates. Moreover, the removal of the metal scaffold is so aggressive that the deformation of desired structures can occur.Ji et al.  also use2 have been studied by Xia et al. [2/g, the sorption capacity was achieved for the temperature of 77 K and the pressure of 1 bar, amounting to 0.75 wt.%.Spatial structures with different pore sizes  resulting from thermal activation in the presence of COa et al. . With th2/g can be obtained for example as a result of combustion of sodium ethoxide. Lyth et al. [Graphene foams with a specific surface area reaching even over 1250 mh et al.  reported2/g, which at a temperature of 77 K and a pressure of 1 bar obtained a sorption capacity of 0.85 wt.%. That material was compared with other microwave-exfoliated GOs as depicted in Structures known as graphene sponges are obtained, for example, using the technology of freeze drying  and a GO2/g and pore volume of 1.82 cm3g−1.Spatial porous graphene can be manufactured directly from graphitized coal through multistage processes that involves multiple thermal exfoliation, liquid intercalation, and chemical activation. With such procedure Sun et al.  reached Big family of methods used for the sake of spatial graphene synthesis involves various types of pillars introduced between the graphene planes. Such modification can be based on long-chain polyamides bonding to graphene via amidation , polyeth2/g) and a ten-fold increase in the pore volume [The own research of the authors of this review also focused on a solution with high potential for industrial production of spatial graphene, i.e., using commonly available methods. In their novel 2-step approach, they proposed the use of hydrazine not as a reducing agent but as a compound that cross-links the graphene oxide suspension. This original concept was first confirmed experimentally on a model material-monolayer, quasi-monocrystalline metallurgical graphene HSMG , from whe volume . It shou2/g. In the case of additional decoration of such complex structures with lithium, estimated hydrogen storage capacity may rise to 9.1 wt.% at 77 K and 1 bar [Computer simulations on graphene pillared with fullerenes show that at cryo temperatures, the hydrogen uptake of such structures may reach 4.0 wt.% at 1 bar and 10.3 wt.% at 100 bar , when thnd 1 bar .2 calcinated in 600 °C in nitrogen atmosphere to remove PMMA. The SEM images depicting stages of composites formation are presented in Obviously, the idea of decoration of spatial forms of graphene is under careful investigation. One of the possible approaches involve electrostatic assembling and poly (methyl methacrylate) (PMMA) template . GO-COOH2/g for which hydrogen sorption was carried out at a pressure of 20 bar. About 2 wt.% of Pt nanoparticles were placed on the surface and in the porosities of this material. At cryogenic temperatures, the selected material performed worse than its undecorated counterpart (sorption decreased by about 7–8%), however, at room temperature, an improvement of nearly 56% was observed. Nevertheless, it should be noted that the highest obtained gravimetric H2 uptake for the temperature of 298 K was only 0.131 wt.%.Kostoglou et al.  decorateAn attempt was made and described also with HSMG metallurgical graphene decorated with SiC solid particles directly in the phase of nucleation and growth on the surface of liquid copper . The preAlthough the amount of hydrogen stored in graphene based materials is still lower than expected, a wide range of investigated solutions  give hope of upcoming breakthrough in the field of introduction of these materials in green, sustainable energy systems.2 might serve as a promising “fuel of the future” in many different fields of industry, mainly because of its benefits over traditional energy sources in social, economic, and also environmental aspects. Because of that, for the past decades, many investigations have been made primarily to find a way to efficiently and cost-effectively store and transport hydrogen to be used as a potential fuel.Hydrogen as an energy carrier and a potential fuel is a sustainable source of energy, that can be produced from a variety of different sources, both renewable and non-renewable. H2 production and supply, its storage for not only stationary but also mobile applications, and further costs of hydrogen used as a fuel. All of these aspects directly depend on many economic factors, the development rate of technologies that will be based on hydrogen, as well as the urgent need to reduce the greenhouse gas reduction caused in particular by the extensive use of fossil fuels. Taking these into consideration it must be noticed that the main challenge before making hydrogen a common source of energy is its storage.However nowadays, scientists list several technological barriers that need to be removed in order to finish using the carbon-based energy and focus on the systems based on more green resources like hydrogen. Among them, important are the aspects of cost-efficient and sustainable H2 storage. Among them, we could list methods based on chemical or physical interactions . However, the true challenge for development of hydrogen adsorbing materials is to ensure the light-weight, light-carrier materials that have a sufficient amount of bonding sites. Hence, a significant amount of interest of scientists is focused on the use of materials like graphite, zeolites, carbon nanotubes, metal organic frameworks, and many others. The graphical representation of advantages and disadvantages of different carbon-based materials planned to use for hydrogen storage purposes is depicted in the Over the past years, many various methods have been proposed to fulfill the needs of sufficient HA significant progress has been made in the development of materials for hydrogen storage of which action will be focused on desorption and absorption properties of nanoscale materials with high specific surface area. Among the proposed solution, one of the promising ways to fulfill the needs of efficient hydrogen storage is the use of graphene-based structures. Authors conclude that spatial graphene decorated not only on the outer surfaces but also inside the porosities, may be a solution for hydrogen storage at ambient temperatures and pressures of at most 5 bars.Working of the technology of mass production of the substrates—GO and/or rGO with a high degree of exfoliation and purity at the level of at least 99.99% C;2/g;Development of chemically durable and mechanically resistant, spatially pillared, nanoporous 3D graphene structures with an active surface of at least 1000 mSelection of effective “spill-over” catalysts with a range of reversible reactions with hydrogen identical to the reversible reaction of graphene–graphene;Development of a technology of spatial decoration of nanoporous 3D graphene structures with nanoparticles of optimal “spill-over” catalysts.The strategic issues for the industrial scaling of hydrogen storage systems based on materials using graphene are:Such graphene-based material may be a key to unlocking the global usage of hydrogen in mobile applications e.g., automotive industry.


LINE-1 (L1) is a class of autonomous mobile genetic elements that form somatic mosaicisms in various tissues of the organism. The activity of L1 retrotransposons is strictly controlled by many factors in somatic and germ cells at all stages of ontogenesis. Alteration of L1 activity was noted in a number of diseases: in neuropsychiatric and autoimmune diseases, as well as in various forms of cancer. Altered activity of L1 retrotransposons for some pathologies is associated with epigenetic changes and defects in the genes involved in their repression. This review discusses the molecular genetic mechanisms of the retrotransposition and regulation of the activity of L1 elements. The contribution of various factors controlling the expression and distribution of L1 elements in the genome occurs at all stages of the retrotransposition. The regulation of L1 elements at the transcriptional, post-transcriptional and integration into the genome stages is described in detail. Finally, this review also focuses on the evolutionary aspects of L1 accumulation and their interplay with the host regulation system. Dispersed DNA repeats of LINE-1 (L1) retrotransposons account for 17% of the human genome . HoweverA full-length L1 copy is about 6 kbp. It contains a bi-directional promoter in the 5′UTR; two open reading frames, namely ORF1 and ORF2, and a 3′UTR with a polyadenylation signal (polyA)  12,13,1,113,14. L1 is distributed in the genome via the target-site primed reverse transcription (TPRT) mechanism  20,25,2,225,26. L1s belonging to the LINE class of mobile genetic elements are found in the genomes of animals and plants ,52. AlthA high diversity of ancient L1 families was found in the lancelet, sea urchin, and tunicates, and despite their variability, they make up a small proportion of the repeated sequences ,54. MobiSpermophilus tridecemlineatus from the superorder Afrotheria, perissodactyls, and sigmodontine rodents [In mammals, many LINEs lost the ability to spread due to various mutations and truncations of full-length copies ,72. Only rodents ,78,79,80Mus musculus) differ from the general tendencies of mammals, including humans and other primates, because LINE elements are quantitatively inferior to LTR repeats in its genome [L1 is active in rats and mice. However, the accumulation and activity of mobile genetic elements of the widely studied mouse  ago and are characterized by the distribution of the L1PA-L1PB families ,84,85. CThe branch of great apes split off about 26 myrs ago . Among tHomo sapiens sapiens) and related subspecies, ancient hominids,  are poorly understood due to the difficulties of genomic mapping of repeat elements using short reads available from the sequencing of ancient DNA. Nevertheless, several studies carried out an analysis of the mobile elements, which showed the presence of introgression of the L1 insertion loci of ancient people in the DNA of modern people, the nature of which corresponds to the same for SNV [A number of studies have shown that the accumulation of loci containing L1 repeat insertions is not random but occurs in accordance with functional significance. Thus, L1 insertions are more often retained in the trans-orientation relative to the gene, while insertions in the cis-orientation are washed out from the genome ,97. The  for SNV ,99. More for SNV . An analAnalysis of L1 insertions in modern world human populations of the Phase3 data release project 1000 Genomes, which included 2.5 thousand individuals from 26 populations, reveals 2.91 thousand polymorphic L1 loci . In bothAPOBEC3 protein family and the Piwi-interacting RNA (piRNA)-signaling pathway are involved into the cellular defense mechanisms against the uncontrolled spread of L1 (see Regulation of L1 Activity). One of the most susceptible proteins to strong evolutionary selection, amplification, and divergence in mammalian genomes is the APOBEC3 subfamily of antiviral factor genes [APOBEC3 was noted in the genomes of bats and primates [AID/APOBEC family have lower evolutionary rates in mammals [APOBEC3B  and PIWIL2 genes in human pluripotent stem cells, compared to the closest non-human primates (Pan troglodytes and Pan paniscus). The study showed that L1 silencing in human cells is more efficient as compared to chimpanzee cells [The L1 regulatory factors are evolved along with evolution of L1 elements. or genes ,103. Higprimates ,105,106. mammals . High ev mammals . The dif mammals ,110,111.ee cells .Further, the factors regulating L1 elements are considered in detail.The process of the regulation of L1 activity throughout ontogenesis is complicated. In most cells, L1 activity is inhibited at all stages of the retransposition process in various ways: by decreasing the availability of DNA using DNA methylation ,113,114,DNMT1 and DNMT3B, the knocking out of which leads to the death of mouse embryos [DPPA2 and DPPA4 have been shown to stimulate the expression of the active L1 families (L1Md_T and L1Md_A) and the Dux gene (MERVL repeat transcription factor) in mice at the 2-cell embryo stage [DPPA2 and DPPA4 leads to the loss of the active chromatin marker H3K4me3 and gain de novo DNA methylation of developmental genes and young L1 [Dux and to increased expression of rRNA [The regulation of the L1 element activity in germ cells and during embryogenesis has been most thoroughly studied on model objects such as mice . DNA met embryos ,141 and  embryos . DNA met embryos . It has  embryos . Accordi embryos ,144,145.yo stage . The lacyoung L1 . At pres of rRNA .Prmt5 plays an important role in the repression of retrotransposons in primordial germ cells and in preimplantation embryos in mice. Despite repression of L1 in germ cells, in mouse preimplantation embryos, Prmt5 implements the control of IAP elements by histone methylation H2A/H4R3me2s, migrating from cytoplasm to the nucleus during the period of 2.5–3.5 embryonic days (E2.5–3.5) [G9a, and SETDB1 [G9a plays an important role in the mono and dimethylation of H3K9me1/me2 histones at an early stage of embryo development and germ cells, and its knockout leads to the death of mouse embryos between E9.5 and E12.5 [Suv39h1 and Suv39h2 genes in the mouse and human genomes that replace one another, and only double knockout of the genes leads to mortality after E12.5 [Zcchc8 [Zcchc8 factor in mice increases chromatin availability and L1 expression, resulting in impaired blastula formation and decreased survival of homozygous knockout mice [However, the L1 activation is short-term. In hypomethylated preimplantation mouse embryos, the inhibition of different families of retrotransposons occurs by histone methylation H3K9me3, H3K9me2, H3K27me3, and H4K20me3, mediated by histone chaperone chromatin assembly factor 1 (Caf-1) . The kno2.5–3.5) . Methylad SETDB1 ,149,150.nd E12.5 . Suv39h nd E12.5 . There aer E12.5 ,152. Meter E12.5 . Represser E12.5 ,154. Theer E12.5 . Silencier E12.5 . To reprer E12.5 . In addier E12.5 ,158. A ser E12.5 . Marker er E12.5 . At the er E12.5 . This maer E12.5 ,162. A ler E12.5 ,162. Pos [Zcchc8 . Knockouout mice .The formation of primordial germ cells (PGS) in mice occurs on E7.25  163,164,166,167.Miwi (PIWIL1), Mili (PIWIL2), and Miwi2 (PIWIL4). In contrast, in humans, there are all four proteins: HIWI (PIWIL1), HILI (PIWIL2), HIWI2 (PIWIL4), and HIWI3 (PIWIL3) [Miwi2–piRNA in the mice embryonic male germ cells [Mili and Miwi2) are associated with L1 activation of retrotransposons, impaired cell formation, and infertility. As previously mentioned, Prmt5 is involved in the inhibition of retrotransposons, including L1, in PGS [Prmt5 occurs using two pathways: (1) the methylation of histones H2A/H4R3me2s in the nucleus and (2) the enzyme entrance into the cytoplasm and activation of the piRNA/PIWI-signaling pathway [Prmt5 enzyme migrates into the cytoplasm and provides arginine methylation in Piwi proteins, which is necessary for binding to proteins containing the Tudor domain [Prmt5 knockout in PGS results in complete sterility of the female and male individuals [Prmt5-dependent histone methylation has been shown to be catalyzed by the Fancd2 factor, one of the most important factors for homologous DNA recombination and repair involved in the suppression of L1 in somatic tissues [Fancd2 factor leads to a decrease in Fancd2-catalyzed H2A/H4R3me2s markers in the L1 region at E10.5 [Prmt5 [Mili protein expression begins from E12.5 and lasts the longest until around the spermatid stage in adult testicles [Mili is located mainly in the cytoplasm and is required for the primary processing of piRNA, secondary piRNA biogenesis, the ping-pong cycle, de novo DNA methylation, and post-transcriptional inhibition of L1 retrotransposons [Mili, Mov10L1 [Tdrd1 [Tdrkh (Tdrd2) [Mili is the Rhox10 transcription factor [Rhox10 gene is present only in the genomes of mice, the contribution of the Rho family to the regulation of Piwil2 is evolutionarily conservative according to the authors of the publication [Miwi2 is observed, the protein complex of which induces de novo DNA methylation that inhibits the spread of L1 [Miwi2 provides trimethylation of the H3K9me3 histones of active full-length L1 and LTR elements [Tdrd1 [Mvh [Tdrd12 [Fkbp6 [Gtsf1 [Miwi2 from the nucleus to the cytoplasm, and also lead to the impairment of various retrotransposons and L1-silencing in the nucleus. The Exd1 factor interacts with Tdrd12 and, with its partial deficiency, also leads to both the disruption of Miwi2 biogenesis and activation of L1 [Tex15 occurs, which affects the methylation of only active L1 and IAP retrotransposons. The exact role of factor Tex15 in such a short period of time is not completely clear. An absence of it does not disturb the biogenesis of piRNA but leads to a decrease in the expression of the Gtsf1 factor associated with both the Mili and Miwi2 proteins [One of the most studied mechanisms of L1 inhibition in male embryonic germ cells is the mechanism that involves the Piwi-interacting RNA (piRNA)-signaling pathway, acting at the transcriptional and post-transcriptional levels ,180,181.(PIWIL3) . L1 degrrm cells ,186. Morrm cells . Damages, in PGS ,187. The pathway . In PGS, pathway . Then, aividuals . Recentl tissues . Knockouat E10.5 . Additio5 [Prmt5 ,190. In esticles . Mili isnsposons . Along w Mov10L1 , Tdrd1 [1 [Tdrd1 , and Tdr (Tdrd2)  are alson factor . Althouglication . In the lication . During ad of L1 . In addielements . Lesionss [Tdrd1 , Mvh [19rd1 [Mvh , Tdrd12  [Tdrd12 , Fkbp6 [2 [Fkbp6 , and Gts6 [Gtsf1  lead to on of L1 ,203. Recproteins ,204. Regproteins . Morc1 dproteins .G9a, plays an important role in L1 repression [Mili, which has the longest expression period in the pre and postnatal period, makes a large contribution to the repression of retrotransposons [G9a and Mili [Mili is known to repress retrotransposons at the post-transcriptional level. Mili can also participate in DNA methylation in combination with Miwi2 in the prenatal period [Mili can interact with Tex15 and this is necessary for the methylation of retrotransposons in germ cells [Suv39h2 methyltransferase is observed, which is involved in the methylation of histone H3K9me3 [DNMT1 and the formation of histone repression markers H3K9me3 during mitosis interacting with various factors that modulate histones [Prmt5 and activation of PIWI proteins at the pachytene stage, and its absence leads to the activation of L1 and AIP retrotransposons, resulting in a decrease in DNA and histone methylation, as well as a deficiency in the piRNA/PIWI-signaling pathway, leading to defective meiosis and sterility [Prmt5 activation and its knockout leads to a decrease in Miwi and L1 activation, disrupting the maturation of spermatogonia in spermatids and leading to infertility [Miwi protein, which is characteristic of mature testicles [Pnldc1 and Tdrkh genes involved in the primary processing of piRNA leads to L1 depression and spermatogenesis defects [In mature mice, L1 is inactive in the stem cells of the testes–spermatogonia but is active in spermatocytes . L1 supppression . In addinsposons . During and Mili . Mili isl period ,207. A rrm cells . Additio H3K9me3 ,208. Thu H3K9me3 . In an e H3K9me3 . At the  H3K9me3 . The Uhrhistones ,213,214.terility ,211. It ertility . At the esticles . The lac defects ,217,218. defects ,220.Zcchc8 factor [Zcchc8 knockout mouse embryos is reduced, the expression of L1 and MERVL is markedly increased at the 4-cell embryo stage, and only half of the embryos reach the blastocyst stage and continue to develop [Control of the retrotransposons activity in female germ cells is different from male germ cells. In the precursors of female germ cells, L1 demethylation occurs gradually starting from E10.5 to E15.5–17.5 ,177. Des8 factor . The sur develop .Tex19.1 and its paralogue Tex19.2 with a high level of expression in embryonic pluripotent cells, the placenta, and testicles are specific for mice and rats, and are not found in humans. Controversial data were obtained regarding factor Tex19.1. According to some reports, Tex19.1 affects the regulation of MMERVK10C repeats and does not affect L1 expression in male germ cells and placenta [Tex19.1 can interact with L1-ORF1 and stimulate both polyubiquitinylation and proteasome-dependent degradation of L1 using UBE2A/UBR2 in the placenta and embryonic stem cells [The list of factors in the regulation of retroelements in the process of embryonic development is constantly updated. Factor placenta ,229,230.em cells .DNMT3B expression [DNMT1, DNMT3A, and DNMT3B [DNMT3B are mainly responsible for de novo methylation in the region of pericentromeric heterochromatin [DNMT1 maintains an inherited DNA methylation profile in dividing cells [DNMT3B enzymes, whose knockout does not impair the viability of human embryonic culture cells, DNMT1 knockout in a culture of human embryonic cells leads to their immediate death [DNMT1 knockout did not lead to their death but rather increased the expression of young L1HS and the closest L1 families (L1PA2 and L1PA3). In contrast older L1 families and other repeats of HERV, SINE, and SVA, despite the absence of methylation, remained silent [YY1 is observed in the brain during embryonic development [DNMT1 recognizes heterochromatin markers H3K9me3 and H4K20me3, which profoundly impacts DNA methylation [Mili) is very weak, its knockout leads to hypomethylation of the regions of L1 promoters in the hippocampus and prefrontal cortex, and affects locomotor and cognitive function, causing hyperactivity and reducing anxiety [In a recent study, L1HS activation was shown in preimplantation embryos and placenta in humans with an expression peak on day E8 of the embryonic development . Previoupression . Featurepression ,235,236.d DNMT3B ,238. DNMhromatin , while Dng cells . Unlike te death . Despited silent . In neurd silent . MePC2 sd silent . On the d silent . The L1 d silent . A high elopment . The YY1elopment ,238,239.elopment . At the elopment . A slighelopment . The repelopment ,110. KAPelopment ,245,246,elopment ,248,249.elopment ,250. Theelopment ,251. Theelopment . DNA methylation ,253. A lhylation ,255,256.In most somatic cells in the organism, L1 is repressed and its activation is associated with various pathologies, such as cancer and some autoimmune and neuropsychiatric diseases ,260,261.Next, methods for the regulation of L1 elements specific to various somatic tissues will be considered .MEPC2, KAP2, sirtuins, and the NuRD complex [MEPC2 in the brain in the prefrontal cortex and striatum [In most normal somatic tissues, L1 is repressed by DNA methylation and specific histone modifications . Current complex ,268,269. complex ,270,271. complex ,276,277. complex ,280,281. complex ,284,285.striatum .SIRT6 gene is the suppression of L1 elements, carried out in two ways [MEPC2, which is involved in the methylation of the L1 promoter region. Knockout of the SIRT6 gene in mice causes a several-fold increase in L1 expression and significantly increases the number of retrotranspositions [SIRT7, has been identified, which also inhibits the activity of L1, mainly concerning young families capable of retrotransposition in both mouse and human cells [SIRT7 promotes the deacetylation of H3K18 histones and the formation of heterochromatin, which results in the association of L1 elements with the nuclear lamin A/C and their repression [SIRT6 and SIRT7 can occur in various somatic tissues of the brain, liver, heart, and many others, including those involved in embryonic development [SIRT6 expression is shown in mice with age, especially in the brain, which leads to an increase in L1 expression and the development of the inflammatory process [SIRT7 can also negatively affect the activity of Suv39h1 methyltransferase through inhibition of SIRT1 [Sirtuin genes are associated with life span and longevity, and are involved in many cellular processes, such as DNA repair, telomere length regulation, anti-inflammatory processes, protection against malignanttumors, cell proliferation, ribosomal and protein synthesis, metabolism, and many other processes ,289,290.two ways . In the ositions . Recentlan cells . Interespression . Represselopment ,267. A d process ,292. SIRof SIRT1 , for whiof SIRT1 .In addition to sirtuins, the nucleosomal and remodeling deacetylase multiprotein complex (NuRD) can lead to the formation of heterochromatin in both somatic and embryonic tissues . This coThere is a large number of cellular factors involved in the restriction and degradation of L1 transcripts at the post-transcriptional level . Some ofRNA interference is an effective way of specific inhibition of L1 elements in somatic cells. Inhibition of L1 in somatic cells is carried out using miR-128, which together with the Ago protein form the RISC complex ,302,303.L1 repression by miR-128 can be processed through different mechanisms: by direct binding to the L1 mRNA transcript in the ORF2 region, leading to subsequent degradation of the transcript ; and by Intracellular antiviral defense mechanisms of the cells also extend to dispersed repeats . In respThe following are various antiviral cell factors that inhibit L1 in somatic cells.In response to a viral infection, the interferon-induced ribonuclease L  synthetase (OAS) -RNase L, RNAse L) is activated, which cleaves cellular and viral RNA . The enzMany studies have confirmed that the strong L1 inhibitor is the MOV10 helicase RNA ,330,331.Three-prime repair exonuclease I (TREX1) is an antiviral enzyme activated in response to interferon type 1 and cleaves nucleic acids . It is aThe SAM domain and HD domain-containing protein 1 (SAMHD1) are some of the most well-known protective factors of innate immunity, inhibiting the replication of viruses and participating in the repression of both L1 and other retroelements . The mecAPOBEC3 protein family is one of the first discovered cellular defense molecules against the uncontrolled spread of L1 [APOBEC3 family  have inhibitory activity against L1 [APOBEC3 occurs at the post-transcriptional level by a deamination-dependent or independent mechanism. Various studies suggest that representatives of the APOBEC3 family of proteins have different mechanisms of inhibition of L1 [APOBEC3 family, which is present only in humans, other types of proteins that are evolutionarily more conservative with deaminase activity are also active against L1: AID [APOBEC1 [APOBEC1 deaminase, similar to other enzymes, is active against viruses and retrotransposons. Interestingly, APOBEC1 acts by a deamination-independent mechanism with respect to L1, while, with respect to other repeats and viruses, it uses a deamination-dependent mechanism [AID [ADARs [APOBEC3, AID, and APOBEC1 deaminases is observed in various somatic tissues and a high level of expression is observed in the connective tissues (blood and adipose tissue); in the organs of the immune, digestive, respiratory, and reproductive systems; and in embryonic stem cells  [ADARs which have a high level of expression in various parts of the brain [The ad of L1 ,353,354.ainst L1 ,358,359.ainst L1 , and conainst L1 ,357,358.on of L1 ,358,360.on of L1 . A diffeon of L1 ,363. hA3on of L1 ,365. In  L1: AID , APOBEC1[APOBEC1 , and ADA[APOBEC1 ,368. APOechanism . AID [36ism [AID  and ADARD [ADARs ,368 alsoand A3G) ,369. Allhe brain .NER) mechanism [NER factors were specified and a possible mechanism for inhibiting L1 retrotransposition was suggested [NER factors leads to an increase in the length of the targeted site duplication [NER genes are associated with diseases of xeroderma pigmentosum (XP) and Cockayne syndrome [At the last stage of retrotransposition, which is the integration into the genome, the inhibitors are proteins involved in the repair of single and double-stranded DNA breaks . It was echanism ,124. Theechanism . The autechanism . Later, uggested . Interessyndrome ,372.ATM gene, mutations in which lead to ataxia-telangiectasia [ATM triggers the factors CHK2, p53, BRCA1, and the MRN complex , involved in the repair of post-replicative DNA and cell cycle regulation factors [ATM enzyme leads to an increase in L1 activity [NER, translesion synthesis, and homologous recombination [A large contribution to the inhibition of L1 is made by factors involved in postreplicative DNA repair. One of the first discovered was the iectasia . In resp factors ,374,375.activity . In respbination . The SLXbination . The facbination ,378. Thubination . At the bination . In addibination ,379,380.bination . The autbination .MYC proto-oncogene is involved in many cell processes and in the regulation of the cell cycle, the defects of which are often found in cancer [MYC binding to the L1 5′UTR represses transcriptional activity. However, this has only been shown for some types of cancer cells [Cell cycle factors are involved in the regulation of L1 activity . Howevern cancer . MYC biner cells . Activiter cells . DUSP1 ier cells .MYC in the L1 5′UTR promoter and 3′UTR region, and acts as an MYC repressor [MYC, CCTCF, FOXA1, NR2F2 and E2F1, etc. Moreover, the authors showed the formation of new binding sites in the case of L1 truncation [In the region of the 5′UTR (+83 to +101) L1HS, there is a binding site for the transcription factor RUNX3 (runt-domain transcription factor). The binding of this factor increases the expression and retrotransposition of L1HS elements. In addition, another RUNX3 binding site is located on the antisense chain of the L1HS promoter (+526 to +508), thus expression also occurs in the antisense orientation of nearby sequences . The traepressor . Moreoveepressor . In the epressor . Its intepressor ,308,398.uncation .MEPC2 and ATM genes [MAPT (microtubule-associated protein tau) gene [GABB45B gene was connected to the death of dopaminergic neurons in Parkinson’s disease [Normally, L1 can be active in the brain ,235,236.TM genes ,113. TheTM genes ,402 and TM genes . HoweverTM genes . TDP-43 TM genes . The proTM genes , ParkinsTM genes , and HunTM genes , and alsTM genes . ControvTM genes , and in TM genes ,50,411. TM genes . DespiteTM genes ,414. In TM genes ,416. Theau) gene ,418. Tauau) gene ,420. Theau) gene ,422,423.au) gene . Anotherau) gene . Mitochoau) gene ,426,427.au) gene ,429,430. disease . A recen disease .The process of regulating the activity of L1 retrotransposons is a complex multifactor orchestra, the coordinated activity of which is extremely important for the healthy development of the organism. Factors that control L1 activity are involved in many biological processes, including cell division, immune response, ageing, and neuronal functions. Many cellular factors are aimed at limiting the activity and repropositions of L1 in genome. A much smaller number of factors positively regulate L1. L1 activity is necessary in some stages of development. The functional role of L1 elemets is intriguing and not yet fully elucidated. Recent studies showed the L1 contribution to the early embryonic development, the inflammation, the cell cycle and cellular senescence. Recently, a major breakthrough has been made in understanding the molecular genetic mechanisms of the retrotransposition and regulation of L1 activity. However, many factors involved in the process of the retrotransposition and regulation of L1 in pathologies are not yet known.Moreover, this research area also has prospects for understanding the pathogenesis and development of therapies for autoimmune and viral diseases, neuropsychiatric disorders, and oncological diseases. The strict regulation of L1 elements during germline and embryonic development, as well as the various defects in L1 regulatory factors have been extensively studied on mouse models. Thus, this provides a foundation for research in human reproduction and embryology. The investigation of genetic factors that regulate L1 activity and their defects is also of great importance in the research of rare and complex diseases and, potentially, modulation of certain disease conditions vis regulation of the retrotransposons.