In recent years, the applications of electron cryomicroscopy (cryoEM) for structural studies of macromolecules were greatly enhanced. These applications now include the structural characterization of puriˆed macromolecules, helical ˆlaments, twodimensional (2D) arrays, and even whole cells. All of this became possible due to the improvements in sample preparation, which preserve a close to native environment for the macromolecules (Dubochet et al. 1981), as well as developments of the microscopes including computer-controlled data acquisition and dedicated data processing (DeRosier and Klug 1968; Crowther et al. 1970a).