At Bell Telephone Laboratories on December 16, 1947, physicists John Bardeen and Walter Brattain attached three flimsy metal contacts to a thin sliver of the element germanium, applied an electric signal, and discovered that the signal emerging from their device was nearly a hundred times stronger than the one that went in. Unveiled a week later to Bell Labs executives, the new solid-state amplifier-soon dubbed a "transistor"-was "a magnificent Christmas present," in the words of research group leader William Shockley, who only a month later conceived an improved version that eventually proved far easier to manufacture.

Fifty years later, transistors have shrunk so dramatically that they are now invisible to the unaided eye. Yet as the crucial ingredients in every microchip, acting as microscopic pumps and valves that regulate the flow of electric current, these minuscule devices continue to have a tremendous impact on almost every aspect of modern life.