The phone call from Stockholm came at 2:00 a.m. Pacific Standard Time on October 7, 2014. Shuji Nakamura was awakened by the Royal Swedish Academy of Sciences informing him that, for his invention of efficient blue light emitting diodes, he had been awarded the Nobel Prize for Physics.

“In the spirit of Alfred Nobel, the Prize rewards an invention of greatest benefit to mankind,” the citation read. “As about one fourth of world electricity consumption is used for lighting purposes, [blue] LEDs can contribute to saving the Earth's resources.” In addition, it continued, “the LED lamp holds great promise for increasing the quality of life for over 1.5 billion people around the world who lack access to electricity grids.” The award was made for a revolutionary invention. “Incandescent light bulbs lit the 20th century, the 21st century will be lit by LED lamps.” A source of illumination more efficient than the light emitting diode would be hard to imagine.

The Nobel Prize was the latest in a long series of surprises for Nakamura. Shuji had known from the start that his LEDs had the potential to replace conventional lights, thus reducing energy usage and carbon emissions. What he had not expected was how dramatic the change would be. And, how his technology would proliferate into areas beyond illumination, such as displays, automobiles, horticulture, and medicine. These days, when Shuji attended giant industry trade fairs like LightFair in North America and Light+Building in Europe, he was amazed by the extent to which his tiny lights had triumphed. “I'm very very happy because my device is everywhere,” he said.

Since 2007, when this book was first published, the market for LED replacements for incandescent and other forms of lightbulbs has mushroomed. According to market researcher Strategies Unlimited, it has soared from $6 million in 2007 to $2.6 billion in 2014, an average annual growth rate of 177 percent. In the much larger LED lighting fixtures market, the figures are $336 million (2007) to $13.8 billion (2014), which is an annual growth rate of 70 percent. Based on a total worldwide lighting market of approximately $80 billion, the penetration of LED lighting is expected to top 25 percent this year (2014). The giants of the industry have long since bowed to the inevitable. At Philips, the world's leading maker of lighting, LEDs were already accounting for over one third of lighting sales by 2014, and the proportion was rising rapidly. The same was true at other lighting manufacturers like Osram. Marketing people had coined an ungainly word to describe the phenomenon: they called it “LEDification.”

Governments around the world were doing their bit by raising standards for energy efficiency. In the United States, in the interests of reducing electricity consumption, the Department of Energy mounted a remarkably effective program to promote solid-state lighting. Unable to meet the new benchmarks, incandescents were effectively banned. Halogens would be next to be replaced, followed eventually by fluorescents. As Haitz's law predicted, the brightness of solid-state lighting kept going up while the cost kept coming down. With economies of scale kicking in, manufacturers slashed the price of their products. Utilities offered subsidies on LED bulbs, making it less painful for people to switch. The cost of a 60-watt equivalent bulb dropped below ten dollars. Consumers were learning new metrics for light. Instead of watts, they rated bulbs by lumens (brightness) and degrees Kelvin (color temperature, from cool to warm).

Retrofitting lightbulbs was evolution. Sooner or later all sockets would be replaced. But LED lighting also promised revolutionary change. Thus far, most lighting fixtures merely substituted LEDs for bulbs and tubes. Now new, radically different-looking form factors for fixtures were emerging with integrated designs. They took advantage of the unprecedented smallness of the new light source.

Creative entrepreneurs were coming up with new things to do with light. “Smart” lighting was one buzzword. A slew of start-ups were experimenting with ways to control lights digitally. They deployed LEDs in networks equipped with sensors and microprocessors to reduce energy consumption (for example, by automatically turning off lights when offices are unoccupied) and increase productivity (for example, by tailoring lighting to the task). Not to be outdone, Philips had introduced a home-use system called Hue. It enabled consumers to vary the color (and color temperature) of the lights in their living rooms remotely from their cell phones, via a Wi-Fi link.

In addition to being smart, light was also seen as a drug. Scientists studied the effects of different wavelengths of light on human circadian rhythms (blue wakes you up, red calms you down). Engineers followed close behind. Before long, the new ability to control light precisely looked likely to bring significant health benefits in hospitals and at home.

Meanwhile, as we will see in the afterword, Shuji Nakamura (together with colleagues at the University of California at Santa Barbara) was not resting on his laurels. Though now entering his seventh decade, he was still leading the way. Shuji had developed a second, even more efficient generation of LEDs. He had also co-founded a start-up company, called Soraa, to commercialize his cutting-edge devices.

In LEDs, much innovation was clearly still to come. The revolution in lighting technology had only just begun.