Membrane potential is generated and maintained by concentration gradients of ions such as sodium, potassium, chloride, and hydrogen. Mitochondrial drives the accumulation in mitochondria of cationic dyes such as cyanines, and the mitochondrial is reduced when energy metabolism is disrupted, notably in apoptosis. Changes in the mitochondrial potential have been described during necrosis, cell cycle and apoptosis. Mitochondrial uptake of dye is a possible source of fluorescence variance. Flow cytometry can be used to estimate membrane potential in eukaryotic cells. Methods using cyanines dyes can detect changes in membrane potential. Immunostep MitoStep uses a cationic dye DilC1(5) (1,1).