Phospholipid onion phases were investigated as biomimetic media for the synthesis of silica in a confined environment. Stable multilamellar nanovesicles incorporating sodium silicate solutions could be obtained. Upon aging, silica condensation occurs in the onion interlayer space while preserving the initial multilamellar organization. The hybrid structure consists of an array of apparently unconnected silica nanoparticles in the 20-30 angstrom size range packed in the vesicular 50 A interlayer space, suggesting that the silica growth was efficiently controlled by its confinement in the onion lamellar organization.