Fusion ordinarily requires multimillion-degree heat, but a bucket-sized device fuses nuclei below freezing. The core of the machine is a lithium tantalate crystal, which generates an electric field when heated. A tungsten needle connected to the liquid-nitrogen-cooled pyroelectric substance focuses this field, such that when the crystal is warmed to roughly —3 degrees Celsius, deuterium ions surrounding the needle get kicked at speeds high enough to fuse with a deuterium- loaded target. Pyroelectric fusion power generators are unrealistic—a single run of the machine produces roughly 10 nanojoules, barely enough to heat a thimbleful of water a few millionths of a degree. Still, the process could lead to palm-sized neutron generators far simpler than conventional devices for use as thrusters in miniature spacecraft or in advanced medical therapies. Physicists at the University of California at Los Angeles report their findings in the April 28 Nature.