Fusion reactions may power the Sun and make life on Earth possible, but duplicating that process on this planet is currently stuck at two ends of an extreme. On the one hand, fusion can be set off instantly in the heart of a hydrogen bomb with enough energy released to blast a city off the map. At the other, fusion can be induced on a lab-bench level at such low energy returns that such a setup was showcased at the General Electric pavilion at the 1964 New York World's Fair, where it regularly fused atoms together for the public.

The hard part is getting these two extremes to meet somewhere in the middle. No, that's not right. The hard part is to get them to meet in the form of a reactor that can generate more energy than it takes in on a sustained, practical, commercial scale.