Despite advances in nanotechnology, it has proved difficult to find a robust “recipe” for the creation of a wide range of sophisticated nanomaterials. However, researchers from the University of California, Los Angeles (CA), have found that they can create complex structures such as cages and filaments using the power of protein symmetry (Proc. Natl. Acad. Sci. 98, 2217–2221, 2001). The researchers engineered a gene construct encoding a fusion protein comprising two symmetric self-assembling proteins—the trimeric protein bromoperoxidase and the dimeric M1 matrix protein of the influenza virus—linked by a short stretch of amino acids. Escherichia coli was used to express the recombinant (fusion) protein, which naturally combines with other copies to form a tetrahedral cage of 12 subunits. Using a fusion protein of two dimeric proteins, linked by an even shorter stretch of amino acids, the researchers could create protein filaments that formed bundles. Todd Yeates, who heads the research team, notes that although cages may eventually prove useful for drug delivery, his priority is to design two-dimensional layers that can be used as biosensors, detectors, or molecular sieves.