Fig. 2.

CryoET schematic. A In cryoET, the ice-embedded specimen, typically shaped as a slab, is tilted through a wide range of angles in the electron microscope and an image is recorded at each angle. B This collection of images around a common axis constitutes a “tiltseries.” C The images in a tiltseries can be computationally aligned to their common axis and reconstructed into a 3D tomogram by weighted back-projection or other methods. D Subtomograms representing a 3D view of individual macromolecules can be extracted from the reconstructed tomogram, then aligned and averaged (Fig. 7). (Partially inspired by Grünewald et al. 2002)