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. Pyronine B powder dye is most commonly used for staining bacteria and mold. Combined with other dyes, such as BioGnost’s Methyl Green powder dye, Pyronine B may be used for staining RNA and malignant plasma cells in the cytoplasm, such as plasmocytes. DNA has a lower affinity to Methyl Green, and Pyronine B has an affinity to RNA, so the nuclei will be stained green, and RNA (plasma cells) red.