Microcapsules with multilayer-thick shells are synthesized by depositing negatively charged nanoparticles around cationic polyamine aggregates crosslinked by multivalent counteranions (see Figure and inside cover). Unique among hollow-sphere preparative routes, this rapid and green synthesis leads to a robust organic/inorganic hybrid structure, applies to a wide spectrum of colloidal species, and permits the non-destructive encapsulation of water-soluble compounds.