Physicists have created the tiniest light-emitting diode (LED) displays ever¹. The image above was shown on a monochromatic display with pixels less than 100 micrometres across, about the width of a human hair. But Baodan Zhao at Zhejiang University in Hangzhou, China, and her collaborators were also able to create an even tinier LED, whose pixels were 90 nanometres wide — the size of a typical virus, and too small to be resolved even by the most powerful optical microscopes. The results are described in Nature today.

LEDs are semiconductors that emit light when an electric current flows through them. The researchers created a semiconductor from a perovskite, a class of materials that includes not only common minerals from the Earth’s mantle, but also ones that are used in advanced solar panels. The perovskite enabled the team’s LEDs to stay bright, even as the pixels were scaled down to microscopic sizes. “Apart from our scientific curiosity, such experiments show that at extremely small sizes, the perovskite LEDs can still hold reasonable efficiencies,” says Zhao. That gives them an advantage over conventional LEDs.