How does a cloud stay cool under direct sunlight––or seem to vanish in infrared? In nature, phenomena like white cumulus clouds, gray storm systems, and even the hollow hairs of polar bears offer remarkable lessons in balancing temperature, color and invisibility. Inspired by these atmospheric marvels, researchers have now created a nanoscale “cloud” metasurface capable of dynamically switching between white and gray states—cooling or heating on demand––all while evading thermal detection.