Terahertz

Good question. Its one that I heard a lot at my civil job this and last summer too. My answers usually are some variety of “really cool, really small stuff” or “waaaay high tech” (decidedly not ‘stain resistant pants’ or ‘leeettle tiny robots’, more on that later), naturally, that didn’t really serve to clarify anything.

So lets look at some difinitions for nanotechnology:
The Engineering department that I’m in defines nanotech as “Engineering on a scale less than 1 micron…”
This is true, but not very helpful to someone who doesn’t already know whats going on. you see, 1 micron is really tiny. A red blood cell is about 7 microns across. The equipment to get to that scale is very expensive, but once you buy it, extremely small scale is easy to achieve. In my microfabrication lab, we’re building a cheesy toy device that has 80nm thick layers on it. 80 nm is ridiculously tiny. and they’re not particularly afraid of letting us touch them. Which indicates either a little misplaced trust, or that they’re reasonably cheap to make.

The National Research council uses my favorite definition “Operating on a small scale to take advantage of the useful properties that occur”
Quantum mechanics takes effect at the nano scale, and so small changes in size/shape can lead to significant changes in behavior:

Colour is a vivid depiction of the way energy is quantized at a small enough scale, and if we can control that quantization we can fine tune all sorts of interesting things.

One last definition of nanotech is sort of an acid test “devices that are small enough that size affects function” This isn’t very helpful to the layman who doesn’t know what the hell is going on, let me clarify, most of the machines we use in daily life are fundamentally the same no matter how big they are. There is no huge difference in the way one of these:

and one of these:

works in real life, both use the reflection and refraction of light to magnify the night sky. If we look at the parts in your computer or the exotic materials that engineers like to play with, we can see that small changes in size can require huge changes in structure in order to do the same function.

Thats what nanotechnology is.