Thiazolyl blue tetrazolium bromide

Thiazolyl Blue Tetrazolium Bromide, often called MTT, is a membrane-permeable dye that initially produces a yellow solution. MTT is converted to MTT-formazan (a dark blue product) by mitochondrial dehydrogenases present in live cells. For this reason, MTT is used as a quantitative indicator in cell proliferation and cell viability assays.