# How Small Is “Nano” Small?

If you follow the latest science and tech news, you know that talk periodically turns to the topic of nanotechnology, which is basically science and engineering conducted at the (really small) nanoscale. What you may not know is just how small the nanoscale really is.

Anyone with a dictionary can tell you that one nanometer = one billionth of a meter. But what does that really mean? Let’s look for a little perspective.

Of Miles and Millimeters

Traditionally, human beings have measured the world in lengths ranging from a few millimeters (the size of a red ant) to a few miles (the distance you can walk in an hour). So a meter we can imagine. It’s the height of a kindergartener.

One-hundredth of a meter, a centimeter, is about the width of your pinkie. And one-thousandth of a meter, a millimeter, is pretty much a large grain of sand. Try to measure anything much smaller than that and you’re going to need a microscope–not to mention some “tiny” terms.

Micro Means a Millionth

One-thousandth of a millimeter–one-millionth of a meter–is called a micron (or micrometer). If you could mark microns off on a ruler, 25 of them would stretch a little less than a thousandth of an inch. Human hairs are generally between 20 and 200 microns wide, while a single strand of a spider’s web is 5 to 10. Many bacteria are just a micron or two long–small enough to stretch out with several friends on your split ends.

Nano Dwarfs That

A nanometer is one-thousandth of a micron–one-billionth of a meter (nanos is Greek for “dwarf”). To imagine how small that is, think of it this way. To find something a thousand times taller than you, you’d have to look at a mountain. That’s roughly the difference between a nanometer (you) and a micron (the mountain). To find something a billion times taller than you–the difference between a nanometer and a meter–you’d have to measure yourself against the sun.

If you were just a few nanometers tall, those bacteria we left stretched out on your split ends would look to you like a stack of skyscrapers. And the width of the human hair they’re lounging on? It would dwarf the highest mountain you’ve ever seen (even if you live in Nepal).

What on earth could possibly be that small? Remarkably enough, two nanometers is roughly the diameter of a DNA helix–just wide enough to encompass the code of life.