Nucleosynthesis is the astrophysical process by which elements are created and distributed throughout the cosmos. This process is primarily driven by nuclear fusion occurring within stars. In the main sequence phase, the core conversion of hydrogen into helium establishes the initial element abundances. As stars evolve and undergo subsequent burning stages, the fusion of increasingly heavier elements, such as carbon and oxygen, continues to build up the stellar material. The formation of elements heavier than iron generally requires extreme conditions found in stellar death events, such as core-collapse supernovae or the merger of compact stellar remnants, where processes like rapid neutron capture synthesize the heaviest stable nuclei. Thus, nucleosynthesis is responsible for generating the majority of the elemental matter observed in galaxies, underpinning the chemical composition of planetary bodies and life itself.