Histopathology is the science or study dealing with the cytological and histologic structure of the abnormal or diseased tissue. Although it refers to the microscopic examination of tissue in order to study the manifestations of the disease. The study of tissues is called Tissue histology and is important to the understanding of how the human body is able to function as a unit. In clinical medicine, histopathology refers to the examination of a biopsy or surgical specimen by a pathologist, after the specimen has been processed and histological sections have been placed onto glass slides. In contrast, cytopathology examines free cells or tissue.