Viability of Cultured Cells - The growth of cultures is largely dependent on the viability of the cells, which can be assessed by microscopic examination of untreated cells or after staining them with substitute chemicals.

Phase contrast microscopy is used to observe cytoplasmic streaming and presence of a healthy nucleus. The reduction of tetrazolium salt test is used to measure respiratory efficiency of cells.

The Fluorescein diacetate test helps to locate the living cells under UV light by the accumulation of fluorescein in the cytoplasm of intact cells. Evan's blue stains the dead or damaged cells.