Used as a vital stain in biological assays to distinguish between living and dead tissues. In cell viability studies, it is reduced by dehydrogenase enzymes in living cells to formazan, producing a red color. This color change allows visualization and quantification of metabolic activity, commonly applied in seed viability testing, microbial growth assays, and cytotoxicity screening. Also utilized in plant physiology to assess root activity and in microbiology for bacterial enumeration. Its ability to indicate cellular respiration makes it valuable in research and quality control settings.