The main thing to know about nanotechnology is that it's small. Really small. Nano, a prefix that means "dwarf" in Greek, is shorthand for nanometer, one-billionth of a meter: a distance so minute that comparing it to anything in the regular world is a bit of a joke. This comma, for instance, spans about half a million nanometers. To put it another way, a nanometer is the amount a man's beard grows in the time it takes him to lift a razor to his face.

Nanotechnology matters because familiar materials begin to develop odd properties when they're nanosize. Tear a piece of aluminum foil into tiny strips, and it will still behave like aluminum—even after the strips have become so small that you need a microscope to see them. But keep chopping them smaller, and at some point—20 to 30 nanometers, in this case—the pieces can explode. Not all nanosize materials change properties so usefully (there's talk of adding nano aluminum to rocket fuel), but the fact that some do is a boon. With them, scientists can engineer a cornucopia of exotic new materials, such as plastic that conducts electricity and coatings that prevent iron from rusting. It's like you shrink a cat and keep shrinking it, and then at some point, all at once, it turns into a dog.

Substances behave magically at the nanoscale because that's where the essential properties of matter are determined. Arrange calcium carbonate molecules in a sawtooth pattern, for instance, and you get fragile, crumbly chalk. Stack the same molecules like bricks, and they help form the layers of the tough, iridescent shell of an abalone.

It's a tantalizing idea: creating a material with ideal properties by customizing its atomic structure. Scientists have already developed rarefied tools, such as the scanning tunneling microscope, capable of viewing and moving individual atoms via an exquisitely honed tip just one atom wide.

"Nano's going to be like the invention of plastic," says Paul Alivisatos, associate director of physical sciences at Lawrence Berkeley National Laboratory's new nanofabrication center. "It'll be everywhere: in the scalpels doctors use for surgery and in the fabrics we wear." Alivisatos already owns a pair of stain-resistant nanopants from the Gap, made from fibers treated with fluorinated nanopolymer. "I spilled coffee on them this morning, and it rolled right off."