The aim of this seminar is to present the basic methodologies of immunocytochemical and immunohistochemical staining, prerequisites for success in their performance and the practical importance of their application in routine practice. The main difference between ICC and IHC is that IHC is performed on tissue without destroying the histological architecture and it is possible to analyze the expression of molecules in the microenvironment as well. Immunochemical staining is a powerful technique routinely used to detect, localize, and quantify (quantify) cellular macromolecules in preserved tissues. Regardless of the specific method used, the first step of this technique is always the selective binding of the primary antibody to its specific antigen. Immunohistochemistry (IHC) is a method used to determine the expression of biomarkers in tissue. It is used for research and diagnostic purposes in pathology and core branches of medicine.