Histology, cytology and other related scientific disciplines study the microscopic anatomy of tissues and cells. In order to demonstrate a good tissue and cellular structure, the samples need to be stained in a correct manner. Eosin Y powder dye is used in various staining methods in microscopy. It is most commonly used as a counterstain to hematoxylin during the HE staining process, one of the most common types of staining used in histology. It provides optimal results diluted in both water and ethanol. Eosin Y is one of the dyes in Pap stain solutions used for staining cytological samples tested for cervical cancer. It is used as a part of many methods, as well as for preparing the Romanowsky stains. Eosin Y is used in concentrations ranging from 0.5%-5% diluted in water or in ethanol.