Resazurin Cell Viability Assay offers a rapid, reliable, sensitive, and cost-effective measurement of cell viability. Its performance is comparable to other commercial resazurin-based kits such as alamarBlue, PrestoBlue, or CellTiter-Blue. Cell growth maintains a reducing cellular environment while growth inhibition makes it oxidizing. Resazurin, a redox indicator, measures cell viability by monitoring conversion of oxidized, non-fluorescent resazurin (purple) to the reduced, highly red-fluorescent (blue) resorufin. The fluorescent (Ex/Em 530-560 nm/590 nm) or colorimetric (Abs. 570-600 nm) signal is proportional to the number of live, metabolically active cells. The ready-to-use, single-step, no-wash, no-lysis, homogenous assay can accurately measure as few as 80 cells. Non-toxic reagents allow long-term kinetic monitoring. The assay is non-radioactive, and non-carcinogenic and compatible with a variety of cell types including bacteria, protozoa, yeast, fungi, or mammalian cells.