Doctorfish (Acanthurus chirurgus), cleared and stained specimen. Clearing and staining, also known as diaphonization, is a process used to reveal internal structure. The specimen is treated with alizarin dye, which stains the bones red, and alcian dye, which stains the cartilage blue. It is then treated with an enzyme (trypsin) which removes most of the tissue leaving behind collagen. The specimen is then stored in glycerine.