So helium is a limited resource. Okay gotcha. So why not take two hydrogen atoms. Take their protons and neutrons. And just fucking start squeezing them together until you get helium?
And I don’t mean in the same way you get H2. Those are still separate from each other.
Others have already mentioned that this is fusion. But the fact that any nucleus with more than two protons exists at all is interesting. E=mc^2 is a well known equation, but not many people understand it’s practical application. If you shove 2 protons and 2 neutrons together to form Helium, the resulting nucleus weighs less than it’s constituent pieces. Where’d the lost mass go? It turned into binding energy. The energy necessary to force two positively charged protons to hang out together without flying apart. And this is part of the energy input necessary to fusion things. Conversely, when we break Uranium apart we get a lot of energy. For the same reasons. Which is how current fission reactors work.
If you really find this stuff interesting do some googling related to fission, fusion, mass defect, and binding energy.
Not the really the “same reason”. Unless that reason is the in both cases, the binding energy per nucleon is increasing. So, for interested people, also look at the binding energy per nucleon curve. Fe is boring…but stable.