Reactive Black 39 serves as a versatile dye with multifunctional applications. It is crucial in biological experiments, aiding researchers in observing and analyzing cell structures, tracking biomolecules, evaluating cell functions, distinguishing cell types, detecting biomolecules, studying tissue pathology, and monitoring microorganisms. Its usage extends beyond basic scientific research to encompass clinical diagnostics, traditional textile dyeing, and novel applications in functional textile processing, food pigments, and dye-sensitized solar cells.