HIV-1 contains a conical capsid built from ~1,500 copies of the viral CA protein, which pack together on a hexagonal lattice and enclose the RNA genome (left). Electron cryocrystallography was used to produce the first unambiguous pseudoatomic model of the hexamers from which the lattice is assembled (right). The hexamers are stabilized by close interactions between the two CA domains of adjacent subunits (shown in different colors). This newly visualized intermolecular interaction is a novel drug target to disrupt capsid assembly, which may prevent the formation of infectious particles.