DNA is a semiflexible polymer. Its structure as a heteropolymer made from the four different nucleotides makes it possible to program specific recognition sites into the chain. We have used the unique structure and programmability of DNA to assemble nanometer-sized constructs, in this case tetrahedra, from oligomeric DNA. Tetrahedra are intrinsically rigid due to their triangulated geometry. We have tested their mechanical properties with AFM. We are in the process of further functionalizing these structures and assembling them into higher-order structures. This type of design of self-assembling submicroscopic building blocks for specific functions holds great promise both for biomaterials design and for possible medical applications, e.g. for drug delivery. (collaboration with A. Turberfield, Oxford)