m-Tolyltetrazolium Red is primarily used in biochemical and microbiological assays as a redox indicator. It is commonly employed in cell viability tests, where it helps to determine the metabolic activity of cells. When metabolically active cells reduce m-Tolyltetrazolium Red, it changes from a colorless or pale yellow compound to a brightly colored formazan product, which can be quantified spectrophotometrically. This makes it a valuable tool in assessing cell proliferation, cytotoxicity, and the effectiveness of drugs or treatments in research and clinical settings. Additionally, it is utilized in plant physiology studies to evaluate seed viability and root activity. Its sensitivity and ease of use make it a popular choice in various laboratory applications.