Widely used in biological and microbiological research as a vital stain to detect cellular metabolic activity. It serves as an electron acceptor in dehydrogenase enzyme reactions, where metabolically active cells reduce it to formazan, a red-colored, insoluble compound. This color change allows for easy visualization and quantification of cell viability, proliferation, and cytotoxicity in assays. Commonly applied in MTT-like assays for screening drug efficacy, toxicity testing, and monitoring microbial growth. Its ability to penetrate cell membranes makes it suitable for both adherent and suspension cell cultures. Also used in environmental microbiology to assess microbial activity in samples.