Space filling models of some protein cages discussed in this review. P22 procapsid (56 nm diameter, T = 7) PDBI: 3IYI, CCMV (28 nm, T = 3) PDB: 1CWP, CPMV (30 nm, pseudo T = 3) PDB: 1NYZ, MS2 (27 nm, T = 3) PDB: 2MS2, Qβ (30 nm, T = 3) PDB: 1QBE, ferritin (12 nm) PDB: 2FHA, sHsp (12 nm) PDB: 1SHS, LS (15 nm, T = 1) PDB: 1RVV, and Dps (9 nm) PDB: 1QGH. These images were reproduced using UCSF Chimera (http://www.cgl.ucsf.edu/chimera) from the Resource for Biocomputing, Visualization, and Informatics at the University of California (supported by NIH RR-01081).