A) Schematics of Gag polyprotein domain organization, including the cleavage pathway leading to viral maturation. Reprinted with permission from Han et al., J. Am. Chem. Soc., 2013, 135, 17793–17803. Copyright 2013 American Chemical Society. B) Artistic representation of structural differences between immature and mature HIV-1 virions. Reprinted with permission from Monroe et al., Structure, 2010, 18, 1483–1491 [111]. Copyright 2010 Cell Press. C) Electron micrograph image of HIV-1 virions. Both immature and mature virions are visualized here. Reprinted from open access V. Baumgartel et al., Viruses 4 2012 777–779 [112].