A review of the political and technical challenges faced by the International Thermonuclear Experimental Reactor (ITER) as it faces a decisive stage in its future.
Officials are currently deciding where to site the world's first big nuclear fusion reactor as part of the International Thermonuclear Experimental Reactor (Iter) project.
China and the US are officially joining the International Thermonuclear Energy Reactor project, the largest international science project of the next decade - excepting the International Space Station.
Five years after pulling out of an international project to develop cheap, safe, renewable fusion energy, the US has announced plans to return.