In this contribution, we present the highly ordered inner structure of crosslinked poly(ionic liquid) nanoparticles. Cryogenic transmission electron microscopy revealed that they resembled centric multilamellar vesicles of different geometries, depending on the exact length of the quaternizing alkyl chains. The nanoparticle size was found to be sensitive to the polymerization conditions, such as the concentrations of monomers and crosslinking agents, the anion type and the externally added salt, but fairly inert to the polymerization temperature and the amount of initiator. The size expansion of the nanoparticles in different polymerization runs was found to be either isotropic or anisotropic via their linear attachment under certain polymerization conditions.