Beta-galactosidase at 3.2 angstrom resolution illustrates the differential effect that electron radiation (orange rays) has on different parts of proteins (green) during high-resolution cryo-electron microscopy (cryo-EM) imaging. Acidic side chains, like glutamate (bottom, red atoms), break down first, before more basic side chains, like histidine (top, blue atoms). Beta-galactosidase is an enzyme occurring in certain yeasts and in the intestinal juices of mammals, especially one that catalyzes the hydrolysis of lactose into glucose and galactose. Created by Veronica Falconieri and Sriram Subramaniam, 2014.