Flow cytometry is the measurement of physical and/or chemical characteristics of large populations of single cells or other biological particles in a fluid stream directed through the path of laser beams. An extended function of flow cytometry is cell sorting. Cell sorters are capable of separating cells or other particles according to one or more user-specified properties into tubes or plates. In recent years flow cytometry has been developing rapidly and is used extensively in all fields of biological science because of its speed, accuracy, and varied applications.