Pigment Red 21 is a multifunctional dye used in biological experiments to help researchers observe and analyze cell structures, track biomolecules, evaluate cell functions, distinguish cell types, detect biomolecules, study tissue pathology, and monitor microorganisms. Its applications span from basic scientific research to clinical diagnostics. Additionally, dyes are widely employed in traditional fields like textile dyeing, and in emerging fields such as functional textile processing, food pigments, and dye-sensitized solar cells.