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. Water Blue dye, known as aniline blue WS or Acid Blue 22 is a component of many polychromatic dyes, such as Heidenhain’s Azan dye and Mann’s dye, as well as various staining methods, such as Mallory, Masson, Gomori polychromatic staining methods, and Lendrum’s MSB technique. Water Blue is used as a counterstain in histology and cytology, as well as the pH indicator (pH 10.0-13.0). Water Blue can also stain histones, that being the standard method of determining the maturity of a nucleus. The activity of sperm is also determined using the Eosin-Water Blue dye.