4-Aminodiphenylamine sulfate (Variamine Blue RT sulfate) serves as a multifunctional dye with extensive applications in both scientific and industrial domains. In scientific research, dyes assist in observing and analyzing cell structures, tracking biomolecules, evaluating cell functions, differentiating cell types, detecting biomolecules, studying tissue pathology, and monitoring microorganisms. Their utility extends from basic research to a broad spectrum of clinical diagnostics. Additionally, dyes find significant use in traditional sectors like textile dyeing and in emerging areas such as functional textile processing, food pigments, and dye-sensitized solar cells.