Fluorescein isothiocyanate (FITC) is widely used as a fluorescent dye in biological and chemical research. Its primary application is in labeling proteins, antibodies, and other biomolecules for fluorescence microscopy, flow cytometry, and immunofluorescence assays. FITC binds covalently to amino groups, enabling the visualization and tracking of specific molecules within cells or tissues. It is also employed in diagnostic tests, such as detecting antibodies or antigens in clinical samples. Additionally, FITC is used in environmental monitoring to trace water flow and contamination due to its strong fluorescence under UV light. Its versatility and high sensitivity make it a valuable tool in both research and industrial applications.