A young boy playing in a squatting position<unk>  involves the biological, psychological and emotional changes that occur in human beings between birth and the conclusion of adolescence.<unk> hood is divided into 3 stages of life which include early<unk> hood, middle<unk> hood, late<unk> hood ( preadolescence). Early<unk> hood typically ranges from infancy to the age of 6 years old. During this period, development is significant, as many of life's milestones happen during this time period such as first words, learning to crawl, and learning to walk. There is speculation that middle<unk> hood or ages 6–13 are the most crucial years of a<unk> 's life. Adolescence is the stage of life that typically starts around 15 years of age, all the way up until legal adulthood. In the course of development, the individual human progresses from dependency to increasing autonomy. It is a continuous process with a predictable sequence, yet has a unique course for every<unk> . It does not progress at the same rate and each stage is affected by the preceding developmental experiences. Because genetic factors and events during prenatal life may strongly influence developmental changes, genetics and prenatal development usually form a part of the study of<unk> . Related terms include developmental psychology, referring to development throughout the lifespan, and pediatrics, the branch of medicine relating to the care of<unk> ren. Developmental change may occur as a result of genetically controlled processes known as maturation, or as a result of environmental factors and learning, but most commonly involves an interaction between the two. It may also occur as a result of human nature and of human ability to learn from the environment. There are various definitions of periods in a<unk> 's development, since each period is a continuum with individual differences regarding starting and ending. Some age-related development periods and examples of defined intervals include: newborn (ages 0–4 weeks); infant (ages 4 weeks – 1 year); toddler (ages 12 months-36 months); preschooler (ages 3–5 years); school-aged<unk>  (ages 6–13 years); adolescent (ages 14–19). Promoting<unk>  through parental training, among other factors, promotes excellent rates of<unk> . Parents play a large role in a<unk> 's activities, socialization, and development. Having multiple parents can add stability to a<unk> 's life and therefore encourage healthy development. Another influential factor in<unk> ren's development is the quality of their care.<unk> -care programs may be beneficial for<unk> hood development such as learning capabilities and social skills. The optimal development of<unk> ren is considered vital to society and it is important to understand the social, cognitive, emotional, and educational development of<unk> ren. Increased research and interest in this field has resulted in new theories and strategies, with specific regard to practice that promotes development within the school system. Some theories seek to describe a sequence of states that compose<unk> .
Child development
Social emotional development
Motor skill
Child sexuality
Mental environment
Hearing
Sleep and metabolism
Maternal health