Stereology--or how figures for spatial shape and content are obtained by observation of structures in sections.

Stereology is a geometrically and statistically defined body of simple methods for estimating morphological quantities of three-dimensional (3-d) structures from measurements made on two-dimensional (2-d) sections. The straightforwardness and the strength of its theoretical basis is illustrated by some newer methods applied in experimental clinical research. Contrary to expectation, the reduction in information from 3-d structures to 2-d sections brings about only a minor increase in the statistical uncertainty of the central moments of most of the fundamental structural characteristics. The sole exceptions are the number of isolated structures and the degree of connectedness in 3-d space, structural quantities the importance of which is limited to the questions of (neo)genesis and communications, respectively. In general, the overall variation in morphometry is determined more by biological than methodological variation. Therefore, stereology is part of the broad spectrum of modern quantitation techniques the sensible application of which depends primarily on common sense in the experimental technique and in the definition of the biological question. The ease and the simplicity of the measurements contrasted by the still quite elaborate and difficult histological preparations of tissue mean that the automation of the measuring process alone is not sensible.