Synthesis of light nuclei
In the sun, helium is produced (simplifying) by the fusion of 4 hydrogen nuclei. It’s the energy released by the fusion reactions that mainly provides us warmth and light. The stars also synthesize other elements. By fusion reactions of light nuclei, heavier and heavier elements are formed up to iron. Then the fusion stops, because the formation of heavier nuclei require external inputs of energy.
IN2P3