Organosilica nanoshells with a thin silica cross-link and large internal cavity have been prepared via the miniemulsion periphery polymerization (MEPP) process. Triethoxysilyl-terminated triblock copolymer surfactants were used to stabilize an oil-in-water miniemulsion. Subsequent cross-linking of the terminal silyl functionality yielded hybrid (organosilica) hollow nanoshells. The unique structural design of the shells (large internal cavity and thin porous cross-link) ensured an interesting combination of properties, including high thermal stability, high efficiency of encapsulation, and trans-shell diffusion of ions.