Nanotechnology arrived with the Borg.

We didn�t hear about nanotechnology in the original series. That wasn�t discussed much in the real world of science and engineering. Richard Feynman, in a fairly famous lecture some time in the early 1960s, asked the question; 'How small can a machine be and still be a functioning machine?' People didn�t really seriously start to investigate that question until the 1970s and �80s.

Then it became a very active area of research thanks to people like Eric Drexler and some others who actually started to develop techniques for assembling very, very, very small, microscopic machines and potentially, for building machines from the ground up, atom by atom, molecule by molecule. This became known as nanotechnology � nano being the prefix for a billionth in the metric system.

A lot of science fiction stories started to appear describing what could be done if we built machines that were so small that they would fit inside a blood cell and so forth. So, when the Borg were introduced on the Next Generation and we saw that they use some bizarre technique for assimilating human beings and turning them into drones, someone decided that nanotechnology might be the appropriate thing involved in that process.

But it became clear that when the Borg inject these tubules into your arms they must be sending something more than a drug in to your arm because it started to transform the unfortunate victim in to a machine. Someone decided; 'Let�s say that these are "nanites".' These are little sub-microscopic machines that go in and start infusing your tissues with Borg technology and slowly but surely turning you into a drone.