Used extensively as a fluorescent labeling reagent in biochemistry and molecular biology for tagging proteins, antibodies, and other biomolecules. It enables visualization and tracking of these molecules in techniques like fluorescence microscopy, flow cytometry, and immunoassays. Its isothiocyanate group reacts with primary amines, forming stable thiourea bonds for covalent attachment. Commonly applied in diagnostics, cellular imaging, and research to study molecular interactions, localization, and dynamics in biological systems.