In order to make the tissue suitable for examination, it undergoes a process called formalin fixation and paraffin embedment (FFPE). This process embalms the tissue so ultra-thin tissue slices can be cut, stained and applied on glass slides for viewing under a light microscope. Microscopic examination is performed by pathologists, expert doctors who are trained to identify thousands of different types of cancers. Typically, only a small portion of the tissue is used up for diagnosis, the rest is filed away and kept in the archives of pathology departments and healthcare facilities.