Figure 1. An electron cryomicrograph of rapidly frozen and unstained Campylobacter flagellar filaments (a) contains three-dimensional information, but this has been projected onto two dimensions.

Segments of these filaments (such as shown by the red box) may be aligned to provide the different views needed to generate a three-dimensional reconstruction (Galkin et al., 2008b), shown as a solid surface in (b). The interpretation of such medium- or low-resolution structures frequently requires high-resolution structures of the component subunits.