Scheme 1. Schematic representation of the MicroED technique. (A) The grid samples are placed in a cryo-holder and inserted into the cryo-electron microscope. Diffraction tilt series of crystals are collected during sample rotation. (B) Diffraction frames of a crystal grain. (C) The electron density and crystallographic conformation (D) solved from diffraction data of remdesivir form II (top) and form IV (bottom).