When a laser beam hits a cell or particle as it passes by, it creates both forward and side light scatter. Forward scatter provides information about the cell's size since the laser light is diffracted around the perimeter of the cell. For example, monocytes have a higher light scatter than lymphocytes due to their larger size.
The side scatter provides information about the cell's granular content and complexity. This same technology is utilized by some hematology cell counters as well. For example, neutrophils have a greater side scatter than lymphocytes because they are more granular.
