http://www.newsweek.com/nuclear-fusion-spherical-tokamak-magnets-pppl-1727965

Researchers at a U.S. government nuclear fusion laboratory say they have found a way to downsize the huge magnets that are necessary for controlling fusion plasma in what they think is another step toward creating a viable fusion reactor.

Nuclear fusion refers to the process of joining two atomic nuclei together to form one, heavier atom. However, the mass of the new heavier atom is slightly less than that of the two individual atoms, and this leftover mass is released as energy that can be harnessed to produce electricity.