“…Their recommendations are the basis of an on-going research program to develop methods and software for 3DEM validation. Early structures included myoglobin (1 PDB ID 1mbn [6,7]), the first structure solved by X-ray crystallography, and small enzymes (2 top 4pti [48], bottom right 2cha [49], bottom left 3cpa [50]). As technologies developed, the archive grew to host examples of tRNA (3 6tna [51]), viruses (4 4rhv [52]), antibodies (5 1igt [53]), protein-DNA complexes (6 top to bottom, 1gdt [54], 1tro [55], 2bop [56], 1aoi [57]), ribosomes (7 1fjg, 1fka, 1ffk [58][59][60]), and chaperones (8 1aon [61])…”