Giemsa stain (/ˈɡiːmsə/), named after German chemist and bacteriologist Gustav Giemsa, is used in cytogenetics and for the histopathological diagnosis of malaria and other parasites.
It is specific for the phosphate groups of DNA and attaches itself to regions of DNA where there are high amounts of adenine-thymine bonding. Giemsa stain is used in Giemsa banding, commonly called G-banding, to stain chromosomes and often used to create a karyogram (chromosome map). It can identify chromosomal aberrations such as translocations and rearrangements.
It stains the trophozoite Trichomonas vaginalis, which presents with greenish discharge and motile cells on wet prep.
Giemsa stain is also a differential stain, such as when it is combined with Wright stain to form Wright-Giemsa stain. It can be used to study the adherence of pathogenic bacteria to human cells. It differentially stains human and bacterial cells purple and pink respectively. It can be used for histopathological diagnosis of malaria and some other spirochete and protozoan blood parasites. It is also used in Wolbachia cell stain in Drosophila melanogaster.