In many experimental situations there is some three dimensional particle that is of interest to the microscopist. To obtain morphometric information about the particle, the microscopist must section some reference space that contains the particle or component of interest, but after sectioning, the reference space and component are reduced to a 2-D sample. This sample no longer contains 3-D structures but only 2-D profiles of the reference space and component.

Stereology can be used to obtain 3-D information from 2-D samples. These samples can be micrographs or digital images, or they can even be the cut surface of the 3-D reference space. The four most basic parameters measured using stereological techniques are volume (3-D), area (2-D), length (1-D), and number (0-D). When measuring these parameters it is often advisable to first measure the density of the component within the reference space, next measure the volume of the reference space, and finally multiply the density by the reference volume to obtain the actual structural parameter.