1- Let’s say we have 1,000 hydrogen atoms in empty space. 2- And for this case only, let’s say 1,000 atoms is the point of fusion under their own gravity. 3- Fusion will create energy. 4- And it will continue until the star explodes or collapses, so in this case it will explode after all hydrogen was converted to let’s say carbon. The thing that is puzzling me is, how many of the 1,000 atoms will be converted to carbon, and how many will be converted to energy? Will we lose part of these atoms forever as energy? And let’s say that the new carbon is unstable, just for that example, like uranium, it can explode and split back to hydrogen atoms, will this mean that we will get the 1,000 hydrogen atoms again? And what about the energy, how much of these become energy again? The full question: Is the process of fusion a process of releasing or storing of energy? And what about fission? I can see energy generated in both cases. Is matter a one-way street to energy?