A nanometre is one millionth of a millimetre. You could get about 50,000 of them across the diameter of a human hair. It's impossible to imagine such a scale, but hold the idea for a second. Scientists may soon be able to compress the power of a laptop into a circuit board no larger than this full stop. Nanotechnology. It's a mind-boggling, fascinating subject - and one that inevitably has its doomsayers: messing about at atomic level may result in self-replicating "nanobots" reducing the world to grey goo in a matter of days (page 8).