Used as a vital staining agent in microbiology and cell biology to assess cell viability and metabolic activity. It serves as an electron acceptor in dehydrogenase enzyme reactions, where living cells reduce it to a red-colored formazan product. This color change allows for easy visualization and quantification of viable cells in assays such as cell proliferation, cytotoxicity, and microbial growth studies. Commonly applied in agar diffusion tests to detect microbial contamination and in plant pathology to confirm tissue viability after sterilization or stress treatments. Its ability to penetrate cell membranes and produce an insoluble colored precipitate makes it ideal for both qualitative and quantitative analysis in research and diagnostic laboratories.