Used as a vital stain in biological assays to assess cell viability. It is reduced by metabolically active cells into a red-colored formazan product, allowing visualization and quantification of live cells. Commonly applied in cytotoxicity testing, microbial growth studies, and plant root assays. Also utilized in dehydrogenase enzyme activity measurements due to its role as an artificial electron acceptor. Its colorimetric response makes it suitable for high-throughput screening in pharmaceutical and environmental testing.