The value of<unk> ing lies in its ability to produce a wide range of hues, allowing cellular components to be easily differentiated. This phenomenon is referred to as the<unk>  effect, or more generally as metachromasia.<unk>  effect Blood film stained with Giemsa showing Plasmodium (center of image), the parasite that causes malaria infections. In 1891<unk>  developed a stain using a mixture of eosin (typically eosin Y) and aged solutions of methylene blue that formed hues unattributable to the staining components alone: distinctive shades of purple in the chromatin of the cell nucleus and within granules in the cytoplasm of some white blood cells. This became known as the<unk>  or<unk> -Giemsa effect. Eosin and pure methylene blue alone (or in combination) do not produce the<unk>  effect, and the active stains which produce the effect are now considered to be azure B and eosin. Polychromed methylene blue<unk> -type stains can be made from either a combination of pure dyes, or from methylene blue that has been subject to oxidative demethylation, which results in the breakdown of methylene blue into multiple other stains, some of which are necessary to produce the<unk>  effect. Methylene blue that has undergone this oxidative process is known as "polychromed methylene blue". Polychromed methylene blue may contain up to 11 dyes, including methylene blue, azure A, azure B, azure C, thionine, methylene violet Bernthesen, methyl thionoline and thionoline. The exact composition of polychromed methylene blue depends on the method used, and even batches of the stain from the same manufacturer may vary in composition. Although azure B and eosin have been shown to be the required components to produce the<unk>  effect, these stains in their pure forms have not always been used in the formulation of the staining solutions. The original sources of azure B (one of the oxidation products of methylene blue) were from polychromed methylene blue solutions, which were treated with oxidizing agents or allowed to naturally age in the case of<unk> . Ernst Malachowsky in 1891 was the first to purposely polychrome methylene blue for use in a<unk> -type stain.
Romanowsky stain
Wayson stain
Bielschowsky stain
Auramine phenol stain
Movat's stain
Feulgen stain
Jones' stain
Alcian blue stain