Highly symmetrical gold nanocages can be produced with a controllable number of circular windows of either 2, 3, 4, 6 or 12 via an original fabrication route. The synthetic pathway includes three main stages: the synthesis of silica/polystyrene multipod templates, the regioselective seeded growth of a gold shell on the unmasked part of the silica surface and the development of gold nanocages by dissolving/etching the templates. Electron microscopy and tomography provide evidence of the symmetrical features of the as-obtained nanostructures. The optical properties of nanocages with 4 and 12 windows were measured at the single particle level by spatial modulation spectroscopy and correlated with numerical simulations based on finite-element modeling. The new multi-step synthesis approach reported here also allows the synthesis of rattle-like nanostructures through filling of the nanocages with a guest nano-object. With the potential to adjust the chemical composition, size and geometry of both the guest particle and the host cage, it opens new routes towards the fabrication of hollow nanostructures of high interest for a variety of applications including sensing devices, catalytic reactors and biomedicine. New concepts We demonstrate a new concept for making hollow nanoscale structures which are central to the advances in many current and emerging areas of technology. Nanocages are hollow and porous nanostructures. The ones made of metal are needed for optics, catalysis, biomedicine, and sensing. But, they are difficult to make. In particular, it is difficult to yield precise nanoscale control of the porosity as well as the composition. We address this challenge by combining inorganic colloidal synthesis and metal deposition on biphasic sacrificial templates. The single-particle spectroscopy and simulation confirm that our approach affords tight control over the morphology and porosity at the nanoscale. Previous approaches to making metal nanocages rely on galvanic replacement reactions and siteselective deposition. They offer control over morphology, but limited control over composition, porosity and scaleup. Our approach provides a simple and general strategy to circumvent these issues. It can be applied to a wide range of materials, and with further developement to any nanorattle-like nanostructures.< Réduire