Traditional heating and cooling systems are energy-intensive, and because they typically run on fossil fuels, they aren't sustainable. By mimicking a desert-dwelling chameleon, a team reported an energy-efficient, cost-effective coating. The material could keep buildings cool in the summers—or warm in the winters—without additional energy. Researchers say this color-changing system could save a considerable amount of energy for regions that experience multiple seasons, while still being inexpensive and easy to manufacture.