Most of the water on Earth is found in the oceans, but it's far too salty to drink. While desalination plants can remove salt and make seawater drinkable, they typically use a lot of energy. Now, researchers have developed a promising new material that could change that. Reporting in ACS Energy Letters, a team of scientists created a sponge-like structure filled with long, microscopic air channels that harness sunlight to turn saltwater into fresh, clean water. In an outdoor test, this simple system"just the sponge and a clear plastic cover"successfully produced drinkable water using only natural sunlight. It's a step toward making low-energy, sustainable desalination more accessible. In an outdoor test, the researchers placed the material in a cup containing seawater, and it was covered by a curved, transparent plastic cover. Sunlight heated the top of the spongy material, evaporating just the water, not the salt, into water vapor. The vapor collected on the plastic cover as liquid, moving the now clean water to the edges, where it dripped into a funnel and container below the cup. After 6 hours in natural sunlight, the system generated about 3 tablespoons of potable water. "Our aerogel allows full-capacity desalination at any size," [researcher Xi] Shen says, "which provides a simple, scalable solution for energy-free desalination to produce clean water."