Transmission electron microscopy (TEM) implies an elaborate preparation protocol that includes: fixation in glutaraldehyde followed by osmium tetraoxide postfixation, specimen dehydration, infiltration, resin embedding, ultrathin sectioning and staining with heavy metal salts. The aim of TEM is to examine the ultrastructure of specimens in ways that cannot be examined using other equipments or techniques. In some cases, when the requirement for TEM were made after tissue collection, useful information can be obtained from reprocessing the formalin-fixed, wax-embedded tissue used for light microscopy.