The three basic steps to prepare a specimen are fixation (preservation), staining, and mounting. Preservation prevents destruction or decay of the specimen as well as inhibiting microbiological growth. Different stains and dyes attach to different parts of a cell, such as the nucleus. Specimens are mounted in a medium that is also a preservative and often covered with a cover slip. “Fixing” a biological specimen retains a reasonably good semblance of the object as it appeared when it was alive. It allows the scientists to observe details of the external and internal anatomy of the specimen.