Nature produces a wide variety of exquisite mineralized tissues fulfilling diverse functions, often from simple inorganic salts. Organisms exercise a level of molecular control over the physico-chemical properties of inorganic crystals that is unparalleled in today's technology. This reflects directly or indirectly the controlling activity of biological organic surfaces that are involved in the formation of these materials. Biological materials are intrinsically nanoscale. Biomineralization occurs within specific nanoenvironments, which implies stimulation of crystal formation at certain interfacial sites and relative inhibition of the process at all other sites. Our approach to artificial crystallization is based on the combination of the two latter concepts—i.e., the use of organized organic surfaces patterned with specific initiation domains on a nanoscale to study and orchestrate the crystallization process. This bio-inspired engineering effort made it possible to achieve a remarkable level of control over various aspects of the crystal nucleation and growth, including the precise localization of particles, nucleation density, crystal sizes, morphology, crystallographic orientation, arbitrary shapes, nanostructure, stability, and architecture. The ability to construct large, defect-free, patterned single crystals with controlled nanoporosity; periodic arrays of uniform, oriented nanocrystals; or films presenting patterns of nanocrystals offers a new, bio-inspired nanotechnology route to materials engineering. © 2005 Lucent Technologies Inc.