A method for measuring components or structural elements of cells, primarily by optical means. In flow cytometry, a cytometer, a device for counting cells, projects a beam of laser light through a liquid stream containing cells or other particles. When the intensely focused light strikes the stream, cellular elements give out signals that are picked up by detectors. The signals are converted for computer storage and data analysis, which eventually yield information about various cellular properties. The biophysical properties of the cells in the stream can be measured at rates exceeding 1,000 cells per second. Because cytometry allows many cells to be studied quickly, irregular cells can easily be identified.