Companies have been racing to slim down LED backlights as devices get ever thinner, but the University of Washington may have just beaten everyone to the finish line. Its scientists have developed an LED that, at three atoms thick, is easily the thinnest LED to date -- in fact, it's impossible to build something thinner using current knowledge. The key ingredient is tungsten diselenide, the thinnest known semiconductor. A single sheet of the material is less than a tenth as thick as a conventional LED, but still emits measurable light. It's flexible and strong, too. On a basic level, the technology could be handy for optical circuits, nanolasers and other areas where miniscule lighting is necessary. However, the researchers also see uses for their LED in mobile devices -- it could end up in wearables and other gadgets where even a slight difference in thickness could make a big impact.