Re: fusion.
I like M0nica's idea (although if it was a choice I'd go with Lucca's)
All the energy we have comes from the Sun. Even coal, which was created millions of years ago out of organic matter. Creatures and plants which only lived because of the sun. Solar panels work because of the energy in visible light, which travels all the way from the sun and gets converted into electrical energy by the panels. But efficiency gets lost all along the line, from the centre of the sun to your panel.
Fusion would replicate the process at the heart of the sun, right here on earth. I can say with 99.9% certainty that the energy giants aren't sitting on the technology, its not viable yet. But when it is, all bets are off.