Used in histology and cytology as a biological stain to differentiate cellular components, particularly in blood and bone marrow samples. Helps in identifying and classifying white blood cells during microscopic examination. Also applied in staining nucleic acids due to its affinity for DNA and RNA, aiding in the visualization of cell nuclei and cytoplasmic granules. Commonly part of Romanowsky-type staining methods, which are essential in diagnostic hematology.