The researchers used a technique called cryo-electron microscopy, in which the virus is first frozen at extremely cold temperatures and then imaged. Biological samples, like viruses, need to be placed in a solvent like a water/salt solution to stabilize them. But before they are hit with an electron beam, they need to be completely dry. This is either done by blotting them dry and then dyeing, which can distort the shape and damage the virus, or by freezing. With cryo-electron microscopy, the researchers can visualize the cellular and protein structures up close without risking damage to them.