The base sequence encoded in nucleic acids yields significant structural and functional properties into the biopolymer. The resulting nucleic acid nanostructures provide the basis for the rapidly developing area of DNA nanotechnology. Advances in this field will be exemplified by discussing the following topics: (i) Hemin/G-quadruplex DNA nanostructures exhibit unique electrocatalytic, chemiluminescence and photophysical properties. Their integration with electrode surfaces or semiconductor quantum dots enables the development of new electrochemical or optical bioanalytical platforms for sensing DNA. (ii) The encoding of structural information into DNA enables the activation of autonomous replication processes that enable the ultrasensitive detection of DNA. (iii) By the appropriate design of DNA nanostructures, functional DNA machines, acting as "tweezers", "walkers" and "stepper" systems, can be tailored. (iv) The self-assembly of nucleic acid nanostructures (nanowires, strips, nanotubes) allows the programmed positioning of proteins on the DNA templates and the activation of enzyme cascades.