Iodonitrotetrazolium chloride (INT) is widely used as a redox indicator in biochemical and microbiological assays. It is particularly useful in the detection of dehydrogenase activity, where it changes from colorless to a red formazan product upon reduction, making it a valuable tool for visualizing metabolic activity in cells. In microbiology, INT is employed to assess bacterial respiration and viability, as it is reduced by active electron transport chains in living cells. Additionally, it is utilized in histochemistry to localize enzyme activity in tissue samples, providing insights into cellular function and health. Its application in cytotoxicity assays also helps in evaluating the effects of drugs or toxins on cell viability.