I know this is one that a lot of people think is inevitable, but I'm not so sure. It's complex and the theory has been around a long time, but no one has managed to succeed with this yet.
The Americans came up with the idea of the Stellarator and the Russians with the Tokamac. Just a little more than a decade ago, ICF was declassified and then there's the Z-pinch machine. So far though, no one is really certain about what has to happen to build one that produces more energy than it consumes.
I'm sure we'd all love a "Mr Fusion" ( Truly one of the coolest things from Back to the future ) but I'd settle for one working fusion reactor that does what science has been promising for half a century.
David.
