You can accuse fusion power advocates of being overly optimistic but never of thinking small. Fusion occurs when two elements combine, or “fuse,” together to form a new, third element, converting matter to energy. It is the process that powers the sun, and the fusion world's marquee projects are accordingly grand. Consider the International Thermonuclear Experimental Reactor (ITER), which a consortium of seven nations is building in France. This $21-billion tokomak reactor will use superconducting magnets to create plasma hot and dense enough to achieve fusion. When finished, ITER will weigh 23,000 metric tons, three times the weight of the Eiffel Tower. The National Ignition Facility (NIF), its main competitor, is equally complex: it fires 192 lasers at a fuel pellet until it is subjected to temperatures of 50 million degrees Celsius and pressures of 150 billion atmospheres.