DNA nanotechnology combines unusual DNA motifs with sticky-ended cohesion to build polyhedral objects, topological targets, nanomechanical devices, and both crystalline and aperiodic arrays. The goal of DNA nanotechnology is control of the structure of macroscopic matter on the finest possible scale. Applications are expected to arise in the areas of X-ray crystallography, nanoelectronics, nanorobotics, and DNA-based computation. DNA and its close molecular relatives appear extremely well suited for these goals. This overview covers the generation of new DNA motifs, construction methods (synthesis, hybridization, phosphorylation, ligation), and a variety of methods for characterization of motifs, devices, and arrays. Finally, the use of DNA nanotechnology as a tool in biochemistry is discussed.