Shuji Nakamura never meant to change the world. All the Japanese scientist wanted was to do some original research, write a few academic papers, make his presence felt. But he ended up revolutionizing the world of light. In 1993, working in isolation at Nichia Chemical, an obscure firm located in the Japanese hinterland, Nakamura invented the bright blue light-emitting diode. It was the first step on the road to a revolutionary new light source that promises to replace the carbon filament bulb patented by Thomas Edison in 1880, which wastes 95 percent of its energy as heat.