The LIVE/DEAD® Yeast Viability Kit combines a novel two-color fluorescent probe for yeast viability, FUN® 1, with a fluorescent fungal surface labeling reagent Calcofluor® White M2R. Plasma membrane integrity and metabolic function of fungi are required to convert the yellow-green-fluorescent intracellular staining of FUN® 1 into red-orange intravacuolar structures; Calcofluor White M2R labels cell-wall chitin with blue-fluorescence regardless of metabolic state.