About the Cover

When a laser heats and compresses this 2 mm capsule to a high-enough temperature and density, the deuterium–tritium fuel that’s inside will ignite. In recent experiments, the resulting fusion reaction has produced more energy than was put into it. With the fundamental physics better understood, researchers are now working toward developing fusion for commercial use. To learn more, see the article by Stefano Atzeni and Debra Callahan on page 44. (Courtesy of Lawrence Livermore National Laboratory/CC BY-NC-SA 4.0.)