These stains became available to pathologists during the 1980’s. They have revolutionized the practice of diagnostic pathology as well as opened new insights into basic research. These stains are usually monoclonal (sometimes polyclonal) antibodies, which are antibodies raised against specific proteins and amplified by cloning. The antibodies are then labeled with a marker which produces brown or red cellular colors. Depending upon the antibody used and the tissue which is stained, the pathologist may use these stains to narrow a differential diagnosis or confirm an initial impression.