Used as a biological stain in microscopy to differentiate tissue structures, particularly in staining mitochondria and cell nuclei. Commonly applied in histology and bacteriology, including use in the Ziehl-Neelsen technique for identifying acid-fast bacteria like Mycobacterium tuberculosis. Also serves as a pH indicator and in the preparation of Schiff’s reagent for detecting aldehydes in tissues. Additionally employed in textile dyeing and as a coloring agent in some industrial applications.