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.

If this vision can be realized,molecular computers could in one swoop destroy the enormous investment by the semiconductor industry in "fabs,"the plants that fabricate chips. The most advanced plants today cost billions of dollars. Not only would molecular computers disrupt what's probably the world's most important manufacturing industry next to cars, they also solve a looming "problem" presented by the laws of nature. Chip makers face physical limits in etching circuits on the wafer-thin material called silicon. One widely accepted estimate says the limits of silicon will be reached by 2014.