Editing Flow cytometry (section)

==== Hydrodynamic focusing ====
{{main|Hydrodynamic focusing}}
For precise positioning of cells in a liquid jet, hydrodynamic focusing is used in most cytometers.<ref name=":1" /><ref name=":2" /> The cells in suspension enter into the instrument enclosed by an outer sheath fluid. The sample core is maintained in the center of the sheath fluid. The sample input rate or how fast the cells flow through to the laser interrogation can be controlled by the pressure of the sheath fluid on the sample core. Under optimal conditions, the central fluid stream and sheath fluid do not mix.{{cn|date=April 2022}}