7-Amino-4-methylcoumarin hydrogensulfate (Coumarin 120 hydrogensulfate; AMC hydrogensulfate) serves as a versatile dye extensively utilized across various domains. This compound plays a crucial role in biological experiments, aiding in the observation and analysis of cell structures, tracking of biomolecules, evaluation of cell functions, differentiation of cell types, detection of biomolecules, examination of tissue pathology, and monitoring of microorganisms. Its applications extend beyond basic scientific research, encompassing both traditional uses in textile dyeing and contemporary usages in functional textile processing, food pigments, and dye-sensitized solar cells.