Used as a red-orange fluorescent dye in histology for staining cells, particularly in H&E (hematoxylin and eosin) staining to color cytoplasm and extracellular matrix for microscopic examination. Commonly applied in pathology to identify tissue structures and detect abnormalities in biopsies. Also serves as a pH indicator, changing color around pH 2 to 4. Used in some ophthalmic procedures to stain damaged corneal tissue for better visualization. Employed in dermatology for evaluating skin conditions under fluorescent light. Acts as a photosensitizer in photodynamic therapy and in some solar cells for light absorption. Found in some inks, cosmetics, and textile dyes for its vibrant color. Used in flow visualization and fluid dynamics studies due to its strong color and solubility.