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. Azure II powder dye is a mixture of Azure B (Azure I) and Methylene Blue dye in equal ratios. It is used for hematologic staining with added Eosin Y stain. The usual color of nuclei (purple) is achieved as a result of molecular interactions between the Eosin Y stain and the Azure B-DNA complex. Staining intensity depends on the amount of Azure II and Azure B/Eosin Y ratio. Several factors may contribute to the results of staining, such as pH solution and buffer solutions, buffer substances, fixation and duration of the staining procedure.