OD600
= OD600
{wiki=OD600}
OD600, or optical density at 600 nanometers, is a measurement used primarily in microbiology to estimate the concentration of cells in a liquid culture. The optical density is measured using a spectrophotometer, which directs light at a wavelength of 600 nm through a sample. The degree to which the light is absorbed or scattered by the cells in the culture is then quantified as optical density.