The interaction between histochemistry and microscopy for quantifying the morphology and function of cells in sections of tissue is reviewed. In principle, the morphological parameters of cells can be measured in suitably-stained sections using image analysers. In practice, however, the individual cells often cannot be distinguished from each other in such systems. This problem might be overcome, at least in muscle, by visualizing types III and IV collagen in the connective tissue and basement membranes surrounding the cells. The functional capacities of cells within tissues can be inferred by measuring the activities of their key enzymes with quantitative histochemical techniques. At present, the wrong enzymes are frequently chosen for this purpose. Flux-generating and physiologically significant enzymes are preferable, but this requires new histochemical techniques to be devised and validated quantitatively for use with the computer-assisted analytical microscopes that are now becoming available commercially.