Author(s): Federica Coppari In this forward-looking PRL Essay, Federica Coppari presents a compelling perspective on high-energy-density science, centering on the remarkable behavior of matter under extreme conditions—such as very high pressures and a wide range of temperatures—like those found deep inside planets, stars, and fusion reactions. [Phys. Rev. Lett. 137, 040001] Published Mon Jul 20, 2026