Stereology is defined as a Discipline consisting of a set of statistical-geometric procedures in order to obtain quantitative information of three-dimensional structures from their two-dimensional images. It becomes a methodological system for the determination of three-dimensional structures by means of mathematical interpretation of histological sections, which uses Mathematics, Geometry, Probabilistic Statistics, and above all, common sense as its main tools. This paper focuses on explaining stereological principles, techniques, grids, sample size and programs. Stereology is a quantitative and comparative method that uses planes, lines and points for the estimation of three-dimensional parameters of morphological structures from two‑dimensional parameters, using isotropy and randomness as prerequisites. Stereology seems to be an applicable tecnique in Health Sciences to mathematically demonstrate the relationship among the components density of a three‑dimensional structure.