Gustav Giemsa was a German chemist and bacteriologist. He is known for his creation of the Giemsa stain, a dye solution named after him. The dye solution consists of methylene blue-eosin and methylene blue. It is used in histopathologic diagnosis, e.g. in staining blood films. Because of the basic and acidic dyes it contains it is favored for use in differential staining. It is capable of differentiating acid and basic granules in granulocyte. When combined with Wright stain, it differentially stains cells, e.g. human cells stain purple whereas bacterial cells stain pink. The stain is also used in histopathological diagnosis of malaria, i.e. when Plasmodium species are observed in stained blood films. Apart from Plasmodium species, it is also employed in staining Histoplasma species, Chlamydia species, and other parasitic protozoans. Giemsa stain is also essential in the field of cytogenetics. The dye is used to stain chromosomes in chromosome banding. The stain attaches to regions that are high in adenine-thymine bonds , resulting in dark bands in the chromosomes. Chromosome banding enables karyotyping and identifying chromosomal aberrations.