For Mark Reed, the future of molecular electronics has just arrived. A self-described "device guy," Reed, who heads Yale University's electrical engineering department, prides himself on having a distinctly practical bent. Ask him about the possibility of one day using molecules to replace silicon in computers that are billions of times faster than today's PCs or that fit on the head of a pin, and he grimaces. "I don't know how to do that. I don't think anyone does," he says dismissively.

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