What is a key technique used in flow cytometry?

In flow cytometry, the primary technique involves separating and analyzing cells based on fluorescent markers. This method allows for the detection and quantification of different cell populations within a mixture by using specific fluorescently labeled antibodies that bind to cellular components. When a fluid containing these cells is passed through a laser beam, the fluorescent markers emit light at varying wavelengths, which is then captured and analyzed to provide data about the size, complexity, and specific characteristics of the cells. This technique is invaluable in various applications, including immunology, oncology, and diagnostics, as it enables rapid and accurate analysis of thousands of cells per second.

Other techniques listed, such as filling syringes with fluid or counting cells manually, do not pertain to the advanced analytical capabilities that flow cytometry provides. Measuring viscosity of fluids, while relevant in other contexts, does not relate to the fundamental processes involved in flow cytometry. The use of fluorescent markers is what distinguishes flow cytometry from other methods, making it a key technique in this field.