“…Crystallography relies on a very low degree of heterogeneity among the many molecules in their unit cells. As one gets to larger structures, one can find a greater range of conformational variations in macromolecules; one can sort for a number of these variations in single particle electron microscopy [52,53,54,55]. Individual variations are seen in the interiors of larger viruses (see for example [43,44]), and by the time one reaches the length scale of bacteria and especially with eukaryotic cells, one has a large degree of structural heterogeneity.…”