What is the principle of flow cytometry?

Flow cytometry is a sophisticated laser-based analytical technique that involves passing cells or particles in a fluid stream through a laser beam. It is used to analyze and measure multiple phenotypic characteristics of single cells. 

Flow cytometry works on the principle of light scattering, excitation, and fluorescence emission. When fluorescently tagged cell components pass through a laser beam, they produce lights of varying wavelengths. Researchers analyze cellular properties based on the fluorescence produced. 

When a particle deflects incident laser light, it produces light scattering. The particle’s physical properties (its size and internal complexity) determine the extent of the light scattering. The cell size or cell-surface area is based on the forward-scattered light, while the internal complexity or granularity of the cell is based on the side-scattered light. These two measurements are used to differentiate different cell types in a heterogeneous cell population.