We have developed virus-based protein cage functional materials for catalysis and optical coatings. The unique properties of the viral particles, such as in vitro reversible self-assembly with functional nanoparticles or molecules incorporated, their capability of chemical or genetic modification and the ability to self-assembly into high-order structures, were employed to introduce new or different functions into these catalytic and/or optical materials. These studies help to gain further insight in the development of virus-based materials.