Histopathological examination of tissues starts with surgery, biopsy, or autopsy. The tissue is faraway from the body or plant, and then. often following expert dissection within the fresh state placed during a fixative which stabilizes the tissues to stop decay. the foremost common fixative is formalin (10% neutral buffered formaldehyde in water). he tissue is then prepared for viewing under a microscope using either chemical fixation or frozen section. If an outsized sample is provided e.g. from a surgery then a pathologist looks at the tissue sample and selects the part presumably to yield a useful and accurate diagnosis - this part is removed for examination during a process commonly referred to as grossing or hack. Larger samples are move correctly situate their anatomical structures within the cassette. Certain specimens (especially biopsies) can undergo agar pre-embedding to assure correct tissue orientation in cassette & then within the block & then on the diagnostic microscopy slide. this is often then placed into a plastic cassette for many of the remainder of the method