Histology: The study of the form of structures seen under the microscope. Also called microscopic anatomy, as opposed to gross anatomy which involves structures that can be observed with the naked eye. Traditionally, both gross anatomy and histology (microscopic anatomy) have been studied in the first year of medical school in the U.S. The word "anatomy" comes from the Greek ana- meaning up or through + tome meaning a cutting. Anatomy was once a "cutting up" because the structure of the body was originally learned through dissecting it, cutting it up. The word "histology" came from the Greek "histo-" meaning tissue + "logos", treatise. Histology was a treatise about the tissues of the body and the cells thereof.