Flow cytometry is a biophysical technology used for cell counting and biomarker detection within a heterogeneous population. It simultaneously measures and analyses multiple physical and chemical characteristics of particles, usually cells, as they flow in a fluid stream through a beam of light. Any suspended particle or cell from 0.2–150 micrometers in size is suitable for analysis, and up to thousands of particles per second can be analyzed. Cells from tissues must be disaggregated before analysis.