Confocal laser scanning microscopy (CLSM) differs from a conventional microscope in that it allows the sample to be observed not in transmitted light, but in reflected light.
To enable the sample to generate its own light, it is stained with various fluorescent dyes, which emit light when they bind to specific molecules: DNA, carbohydrates and proteins. This makes it possible not only to visualise the sample, but also to determine its composition.
Another important advantage of CLSM is that the coherence of the laser beams allows optical sections of the object to be made at the focal plane, cutting off any out-of-focus fluorescence. The result is a highly detailed 3D structure of the object.