Nuclear fission is a process where the nucleus of an atom, such as uranium or plutonium, splits into smaller parts, releasing a significant amount of energy. This reaction is commonly used in nuclear power plants to generate electricity. When the nucleus splits, it also releases neutrons, which can trigger further fission reactions, leading to a chain reaction. Nuclear fusion, on the other hand, occurs when two light atomic nuclei, like those of hydrogen, combine to form a heavier nucleus, such as helium. This process releases even more energy than fission and is the reaction that powers the sun and other stars. Scientists are researching fusion as a potential source of clean and abundant energy.