Imagine a microscopic computer that assembles itself, atom by atom, then calculates at a speed faster than today 's zippiest electronic chips. Now imagine this same computer is unbelievably cheap -dirt cheap, in fact.Sounds too good to be true? Well,some people think it 's real. This is the idea behind nanotechnology: that individual molecules can serve as digital switches and, acting in concert with billions of other molecular switches, replace digital computers.

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