XTT sodium salt is widely used in cell biology and biochemistry for assessing cell viability and proliferation. It serves as a key component in the XTT assay, a colorimetric method that measures the metabolic activity of living cells. When cells are metabolically active, they reduce XTT sodium salt to a water-soluble formazan dye, producing a color change that can be quantified using a spectrophotometer. This assay is particularly useful in drug screening and cytotoxicity studies, as it allows researchers to evaluate the effects of compounds on cell growth and survival. Additionally, its water-soluble nature eliminates the need for organic solvents, making it a safer and more convenient option compared to other tetrazolium-based assays. Its application extends to cancer research, immunology, and microbiology, where it helps in understanding cellular responses to various stimuli.