How do 4 Hydrogen atoms combine to form 1 Helium atom? What I'm looking for is the sub-atomic process. So, here come 4 Hydrogen atoms racing towards each other and they are at such a high speed and temperature that something different happens. Something different than if they were going slower or at a lower temperature. I'm guessing there are unseen particles that are interacting and changing and some flying off and energies being exchanged left and right. I'm just wondering specifics.