High-brightness light-emitting diodes (LEDs) emit visible light at efficiencies competetive with conventional incandescent and fluorescent lamps. The levels of radiant efficiency for conventional white light sources (5–7% for incandescent lamps and 28% for fluorescent ones) are unlikely to increase significantly because of the limits of the underlying physical processes. In contrast, LEDs have the potential for close to 100% power-to-light conversion (theoretically, the effective conversion efficiency could be even higher than 100%, since the LED could take some energy out of the environment). LED lamps are more efficient, longer-lived (100,000 h and more), environmentally friendlier (mercury-free), and more shock-resistant than conventional light bulbs and fluorescent tubes. In addition, LED technologies offer more versatility in the design of lighting fixtures, and digital control of color and light intensity. Over the next 20 years, LEDs are predicted to gradually replace conventional lamps in much the same manner as solid-state circuits replaced vacuum tubes years ago.