The fabrication of nanostructures by biomolecules is proposed. The process utilises biotemplated biomineralisation of inorganic materials and self-assembly, termed the 'bio-nano process' (BNP). Artificial proteins are designed to construct functional nanometric structures in combination with top-down miniaturisation technologies. Genetically modified cage-shaped proteins, ferritin and deoxyribonucleic acid-binding protein from starved cells, are the most studied biotemplates for the BNP. The inner cavity is used as a spatially restricted chamber for the synthesis of homogeneous metal, metal-complex and semiconductor nanoparticles (NPs). Proteins with NP cores are delivered onto specific substrate locations or carbon nanotube surfaces by electrostatic interaction or specific binding peptides. These NPs realise a variety of functions such as charge storage nodes for floating gate memory, catalysts for carbon nanotube growth, quantum wells in heterogeneous junctions and nanoetching masks. Cage-shaped protein-based bioconjugates play an important role and expand the application fields. The BNP is capable of producing functional nanostructures that are otherwise impossible through other methods.