High-dose helium implantation of metals can result in the formation of nanoporous bubble structures with striking features. These structures which may be a universal response for all metals implanted under appropriate conditions, show considerable promise for applications such as catalysis. They are characterized by nanoscale cavities of uniform size, a high degree of swelling and extremely thin metal walls (similar to1 nm in thickness) separating nearest neighbor cavities The internal surface area associated with the cavities is high and the method of production offers the potential for controlling pore size through the selection of implant parameters.