Flow Cytometry Principles

The basic principle of flow cytometry is the passage of cells in single file in front of a laser so they can be detected, counted and sorted.

Cell components are fluorescently labelled and then excited by the laser to emit light at varying wavelengths.

The fluorescence can then be measured to determine the amount and type of cells present in a sample.

Up to thousands of particles per second can be analysed as they pass through the liquid stream.

A beam of laser light is directed at a hydrodynamically-focused stream of fluid that carries the cells.

Several detectors are carefully placed around the stream, at the point where the fluid passes through the light beam.

One of these detectors is in line with the light beam and is used to measure Forward Scatter or FSC.

Another detector is placed perpendicular to the stream and is used to measure Side Scatter (SSC).

Since fluorescent labels are used to detect the different cells or components, fluorescent detectors are also in place.

The suspended particles or cells, which may range in size from 0.2 to 150μm, pass through the beam of light and scatter the light beams.

The fluorescently labelled cell components are excited by the laser and emit light at a longer wavelength than the light source. This is then detected by the detectors.

The detectors therefore pick up a combination of scattered and fluorescent light. This data is then analyzed by a computer that is attached to the flow cytometer using special software.

The brightness of each detector (one for each fluorescent emission peak) is adjusted for this detection.

Using the light measurements, different information can be gathered about the physical and chemical structure of the cells.

Generally, FSC can detect the cell volume whereas the SSC reflects the inner complexity of the particle such as its cytoplasmic granule content or nuclear structure.

Further Reading

Last Updated: Feb 26, 2019

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Mandal, Ananya. (2019, February 26). Flow Cytometry Principles. News-Medical. Retrieved on June 26, 2019 from https://www.news-medical.net/life-sciences/Flow-Cytometry-Principles.aspx.

  • MLA

    Mandal, Ananya. "Flow Cytometry Principles". News-Medical. 26 June 2019. <https://www.news-medical.net/life-sciences/Flow-Cytometry-Principles.aspx>.

  • Chicago

    Mandal, Ananya. "Flow Cytometry Principles". News-Medical. https://www.news-medical.net/life-sciences/Flow-Cytometry-Principles.aspx. (accessed June 26, 2019).

  • Harvard

    Mandal, Ananya. 2019. Flow Cytometry Principles. News-Medical, viewed 26 June 2019, https://www.news-medical.net/life-sciences/Flow-Cytometry-Principles.aspx.


The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News-Medical.Net.
Post a new comment
You might also like... ×
Cytek Biosciences unveils advanced five-laser flow cytometer