Used in cell viability and proliferation assays, particularly in colorimetric tests like the MTT assay. It acts as an electron acceptor in enzymatic reactions, where metabolically active cells reduce it to form a water-soluble formazan dye. This allows direct measurement of cell activity without additional solubilization steps, making it ideal for high-throughput screening in drug development and cytotoxicity studies. Its water solubility reduces assay time and improves accuracy compared to traditional tetrazolium salts.