How does fluorescence-activated cell sorting (FACS) work?

A look at how fluorescence-activated sorting works: 

• Cells or particles are first suspended in a fluid medium such as tissue culture medium or blood. In order to identify and sort specific cell populations, the cells are stained with fluorescent dyes or antibodies that bind to specific molecules on the surface of the cell. 
• The stained suspension is injected into a flow cell and focused into a narrow stream that passes through a laser beam, which excites the fluorescent molecules on the cells and causes them to emit light at specific wavelengths. 
• A series of photomultiplier tubes that act as sensors detect and measure the emitted light at varying wavelengths. 
• A computer analyzes and processes the resulting data and generates a graphical representation of the intensity of fluorescent signal for each individual cell in the sample. 
• Researchers can identify and measure different cell populations based on their chemical and physical characteristics as depicted on the histogram.
• Flow cytometers that are equipped with a cell sorter can further help to separate individual cells physically based on their fluorescent properties.