Telescope optics can be made of mirrors or lenses, but in both cases, they’re bulky and need to follow a strict mathematical curve to focus light. Researchers have shown that it’s possible to make a completely flat lens that focuses light. Traditionally, this has been done with Fresnel lenses, but they distort colors. Their new technique carves tiny concentric rings into a substrate that matches the wavelengths of different colors, allowing a full-color, in-focus image.