Lab & analytical techniques · Reference
What is flow cytometry?
Flow cytometry analyses cells one at a time as they flow in single file past a laser, measuring light scatter and fluorescence to characterise and, in FACS, physically sort them.
How flow cytometry works
In a flow cytometer, cells suspended in fluid are drawn into a narrow stream by hydrodynamic focusing, which lines them up one behind another. As each cell crosses a laser beam, it scatters light in two informative ways: forward scatter relates to cell size, and side scatter relates to internal complexity or granularity. If the cell carries fluorescent labels — typically antibodies tagged with dyes that bind specific molecules — the laser also excites them, and detectors measure the emitted fluorescence at different wavelengths. Many cells are measured per second, building a statistical picture of the population.
FACS — sorting cells
Fluorescence-activated cell sorting (FACS) extends the method to physically separate cells. After a cell is measured, the stream is broken into tiny droplets, each ideally containing one cell.
Droplets carrying cells that match chosen criteria are given an electric charge and deflected by charged plates into a collection tube, so a pure subset can be isolated for further study. This couples real-time measurement to physical selection.
Uses in research
Flow cytometry is central to immunology, cell biology, and microbiology research, where it counts cell types, measures protein expression, and assesses cell health across large populations. It complements bulk antibody assays such as the ELISA by reporting on individual cells. Reliable results depend on careful instrument calibration, compensation between fluorescence channels, and documented gating, so that population analyses are accurate and reproducible.
Key facts
At a glance
- Analyses: cells one at a time in a fluid stream
- Alignment: hydrodynamic focusing (single file)
- Forward scatter: relates to cell size
- Side scatter: relates to internal complexity
- Fluorescence: reports specific labelled molecules
- FACS: physically sorts cells by charged-droplet deflection
Common questions
FAQ
What does flow cytometry measure?+
Flow cytometry measures light scattered by each cell — forward scatter for size and side scatter for internal complexity — plus fluorescence from any labels the cell carries. Together these characterise cell populations one cell at a time.
What is FACS?+
FACS, or fluorescence-activated cell sorting, is flow cytometry that physically separates cells. After measuring each cell, the instrument forms droplets, charges those matching chosen criteria, and deflects them into collection tubes to isolate a pure subset.
The step most authors miss
Doing CRediT right? Don’t stop at the statement.
A CRediT statement credits you inside one paper. The recognition CRediT was built for happens when those roles are tied to you, persistently. Sign in with your ORCID — free — and claim your CRediT contributions on casrai.org, the home of the standard. They become a verified, portable part of your identity, not a line that disappears into one PDF.
Free: claim your contributions, then export a journal-ready CRediT statement, schema.org structured data, JATS XML, CSV or BibTeX — and preview your public profile. A membership publishes that profile publicly and verifies the journals you serve.
