Nanotechnology has been around for two decades, but the first wave of applications is only now beginning to break. As it does, it will affect everything from the batteries we use to the pants we wear to the way we treat cancer.

    The main thing to know about nanotechnology is that it is 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 nanometer. 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 are 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, but the fact that some do is a boon. With them, scientist can engineer a cornucopia of exotic new materials, such as plastic that conducts electricity and coatings that prevent iron from rusting. It is 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 is 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 is 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 exquisitely honed tip just one atom wide.

    In many ways Nano's invention is like that of plastic. It will be everywhere: in the scalpels doctors use for surgery and in the fabrics we wear. When coffee is spilled on a pair of stain-resistant nanopants from the Gap, made from fibers treated with fluorinated nanopolymer, it will roll right off.

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