The XTT Assay utilizes 2,3-bis(2-methoxy-4-nitro-5-sulfonylphenyl)-2H-tetrazolium-5-carboxanilide (XTT) to assess cell viability and metabolic activity. XTT is a tetrazolium compound that is reduced by metabolically active cells into an orange-colored formazan product that can be measured spectrophotometrically. Unlike the MTT Assay, the formazan generated by XTT is soluble in culture medium and does not require an additional solubilization step with DMSO.