Microbial biofilms are complex self-organized communities of microbial cells that provide protective environments for the cells that inhabit the biofilm, enabling them to respond efficiently to challenges. The enhanced resistance and altered metabolism of the cells in the biofilm makes biofilms potentially very useful in chemical production processes, including the production of pharmaceuticals and biofuels. Synthetic biofilms in which the composition and architecture of the biofilm is controlled by the designer could help in harnessing this potential. In this chapter we discuss biofilm architecture, how it can be created by natural or artificial means, and how it affects biofilm function.