Nuclear fusion is the process in which the Sun and all other stars generate energy through the combination of light atoms into heavier ones. The nuclear fusion in most stars is carried out in proton-proton fusion. In the first step, two protons fused together to create a proton-neutron core and emitting a neutrino and positron. Then, the core is fused with another proton to form helium-3. Finally, two helium-3 atoms are combined together to create helium-4 with two additional protons. Since the mass of the final product in this process is lower than the mass of its original components, the “missing” mass was converted into energy. The quantity of this energy can be calculated by Einstein’s famous formula: e = mc^2. Because the speed of light is such a massive quantity, even the most tiny of masses converted into energy will yield very large outputs.