Histopathology is basically the examination of a biopsy or surgical specimen which is done by a pathologist, following the specimen has been processed and histological sections have been positioned onto glass slides. If a large sample is given, For example, the surgical procedure then a pathologist looks at the tissue sample and selects the part which is most expected to yield useful and exact diagnosis - this part is detached for examination in a practice usually known as grossing or cut up. Larger samples are cut to properly situate their anatomical structures in the cassette. Certain specimens (especially biopsies) can experience agar pre-embedding to reassure correct tissue orientation in the cassette and then in the block and then on the diagnostic microscopy slide. This is then positioned into a plastic cassette for the rest of the process.