Immunocytochemistry describes methods for visualization of specific intracellular molecules within cells. These methods use high affinity markers to specifically bind to target molecules in tissues or cells. For electron microscopy, the sites where these markers are bound are visualized using electron opaque probes. Successful immunocytochemistry depends upon immobilization of target molecules, retention of subcellular morphology, and upon total accessibility of affinity marker to the target molecules.

Accessibility to extracellular molecules is not usually a problem, but for intracellular molecules, labeling protocols must be able to preserve subcellular morphology and allow the affinity markers to gain access to their target molecules. Currently, the best way to gain access to the inside of cells for electron microscopy (TEM) is to cut thin sections through them. In this way, morphology is retained and affinity markers can be applied to the cut face of the cells.