Euonymous Scale feeding on a leaf; Histological section
Histologists who study insects at the cellular level may embed an insect in paraffin or plastic then slice the specimen into thin sections to be mounted on a microscope slide and examined. Paraffin was used to embed insects historically, but most modern microscopists embed in a plastic resin. To preserve the insect tissue, the specimen is “fixed”, a process that destroys all enzyme activity that might damage or alter the tissue….
Source: Living With Insects Blog