Rhodamine B isothiocyanate is widely used as a fluorescent labeling reagent in biological and biochemical research. It is particularly valuable for tagging proteins, antibodies, and other biomolecules due to its strong fluorescence and stability. This compound is often employed in fluorescence microscopy, flow cytometry, and immunofluorescence assays to visualize and track cellular components or processes. Additionally, it is utilized in the development of diagnostic tools and in studying molecular interactions, making it a critical tool in both research and medical diagnostics.