The visualization of a gene product, in particular the localization within a biological specimen, is one of the basic topics in cell biology. Applying fluorescence labeling methods molecules can be detected by light microscopy, even in living cells. Nevertheless, the associated morphological structure can be identified in most cases only by electron microscopy. Correlative microscopy allows the comparison of signals at the same position with both imaging methods. We combine cryo immobilization by high pressure freezing with subsequent freeze-substitution and low-temperature embedding in different resins. Thin sections of specimens prepared in this way are used for morphological analysis, including three-dimensional tomography and immunocytochemistry. The important advantage of electron microscopy over light microscopy for antibody labeling is that both partners of the immune reaction, the antigencontaining structure and the bound antibody, can be visualized, allowing much easier determination of specificity and faithful quantification.