Calcein AM is a cell-permeable dye that can be used to determine the cell viability of most eukaryotic cells. In living cells, non-fluorescent calcein AM is converted to green fluorescent calcein following acetoxymethyl ester hydrolysis by intracellular esterases. This dye is also available in our special packaging (C-3100) and 1 mg solid (C-1430). For a longer wavelength version of this dye, check out our new CellTrace Calcein Red Orange AM (Cat. No. C-34851).