Research News: Virus protein rages, capsids, which display a wide range of sizes and shapes, can be used for constrained materials synthesis. The authors briefly review recent work involving capsids, including the use of spherical viruses for inorganic mineralization and organic polymer encapsulation and the mineralization of anisotropic structures such as the tobacco mosaic virus, which can lead to mineralized fibers of iron oxide or silica with very high aspect ratios. The topic of gating-which enables the selective entrapment and release of materials from within the central cavity-is briefly touched upon.