Confocal laser scanning microscopy (CLSM) is a relatively new light microscopical imaging technique which has found wide applications in the biological sciences. The primary value of the CLSM to the biologist is its ability to produce optical sections through a 3-D specimen-e.g., an entire cell or a piece of tissue - that, to a good approximation, contain information from only one focal plane. Article includes principle and applications of confocal laser scanning microscope.