In BIOPSY/FNAC, tissue samples are preserved for immunohistochemistry (IHC) by processes such as fixation, embedding and freezing. Fixation of the tissue sample is essential to maintain cell and tissue morphology during the IHC experiment and during storage. It also prevents the autolysis and necrosis of excised tissues, preserves antigenicity and enhances the refractive index of tissue constituents. The tissue sample is then either embedded in paraffin or frozen. Embedding is important in preserving tissue morphology and giving the tissue support during sectioning. ​​Lastly, a tissue is cut into thin sections usually using a microtome or a cryostat for further analysis.