This energy mostly ends up as heat from which you can make steam to drive turbines and generators, and make electricity in power stations. In the Sun, atoms of hydrogen fuse to create helium and liberate the seemingly endless stream of energy we call sunlight. Without this solar fusion reactor 150 million kilometres away, our home planet would be a frigid lifeless world. Scientists hope to reproduce this fusion reaction in a controlled way to yield almost unlimited energy supplies with far fewer radioactive waste problems. Ironically, Einstein himself never thought nuclear energy would work.
Nuclear energy comes from the tiniest building blocks of matter, the nuclei of the atoms.
It's the number of protons which give the element its chemical identity. An atom with one proton we call hydrogen, the lightest element. Helium has 2. An atom with 92 protons we call uranium, the heaviest of the 92 natural elements which make up our planet. Uranium nuclei also have large numbers of neutrons.