So far, nanotechnology has been limited to material science. The dream of self assembling, communicating, tiny robots that can do all sorts of things (and might turn the world into grey goo) has remained strictly science fiction.
Until now. Scientists at Oxford and Warwick have developed the world's smallest...trains. These tiny robots can build their own tracks, move cargo, and dismantle track that's no longer needed.
The secret? DNA. Nature's programming language is, it turns out, perfectly suited to controlling nanobots. (Which, of course, brings a different apocalypse to mind - the "maker plague" which Alastair Reynolds uses to such effect in Chasm City).
At the same time, these nanobots bring with them great promise. Right now, they don't have as much practical use as one might hope - although some fish use a similar system to change color. But who knows? We might be one step closer to the true replicator. Assembler bots might also be key to constructing a space elevator, which would reduce the cost of getting payload to orbit by orders of magnitude. Or they might be programmed to dismantle tumors better than any surgeon.