Cell markers are a very useful way to identify a specific cell population. However, they will often be expressed on more than one cell type. Therefore, flow cytometry staining strategies have led to methods for immunophenotyping cells with two or more antibodies simultaneously. By evaluating the unique repertoire of cell markers using several antibodies together, each coupled with a different fluorochromes, a given cell population can be identified and quantified. Many immunological cell markers are CD markers and these are commonly used for detection in flow cytometry of specific immune cell populations and subpopulations.