The iPhone 17 Pro and iPhone 17 Pro Max contain thin, hermetically sealed chambers with a drop of water inside that cycles between liquid and gas to help dissipate heat. Known as vapor chambers, the cooling system is becoming more common in smartphones built for sustained high performance. To cool down those hot spots, the industry seems to be moving toward vapor chambers and other phase-change technology. Thin and wide vapor chambers have a high heat-removal capacity and offer an effective solution. Plus, vapor chambers tend to be expensive to manufacture.