Used as a cell viability and proliferation assay reagent, particularly in cytotoxicity and anticancer drug screening. It functions as a tetrazolium salt that is reduced by metabolically active cells into a colored formazan product, which can be quantified spectrophotometrically. The intensity of the color correlates with the number of viable cells, making it valuable in assessing cell metabolism and treatment effects in vitro. Commonly applied in research laboratories for high-throughput screening and in pharmaceutical development to evaluate drug efficacy and cellular response.