In modern times, there is an increasing demand for three-dimensional (3-D) optical microscopy. The main reason lies in the fact that optical microscopy is still unique in its ability to allow the complete three-dimensional examination of biological structures in a hydrated state under experimental conditions that allow the preservation of living or physiological states, also when compared with other high-resolution techniques. This fact coupled with the advent of fluorescence labeling permits the study of the complex and delicate relationships exist in between structure and function in biological systems. One relevant step, in terms of progress in 3-D optical microscopy, was the invention of the confocal microscope in its different solutions. Minsky, in 1957, invented a confocal microscope identical with the concept later developed extensively by Egger and Davidovits at Yale, by Sheppard and Wilson at Oxford, and by Brakenhoff et al. in Amsterdam. It was in the mid-1970s, with the advent of affordable computers and lasers, and the development of digital image processing software, that the first confocal laser scanning microscopes became available in several laboratories and applied to biological and material specimens.