Diatoms are single-celled algae that produce intricately structured cell walls made of nanopatterned silica (SiO2). The cell wall structure is a species-specific characteristic demonstrating that diatom silica morphogenesis is genetically encoded. Understanding the molecular mechanisms by which a single cell executes the morphogenetic program for the formation of an inorganic material (biomineralization) is not only a fascinating biological problem, but also of great interest for nanomaterials science and technology. Recently, analysis of the organic components associated with diatom silica, the development of techniques for molecular genetic manipulation of diatoms, and two diatom genome sequencing projects are providing insight into the composition and mechanism of the remarkable biosilica-forming machinery.