Nuclear fusion is the process by which multiple atoms having the same charge join together in order to form a heavier nucleus. In some cases, depending on the mass, energy can be released or absorbed during this process. Nuclear fusion is a very important energy source.

Nuclear fusion is often confused with nuclear fission. However, the two, while having similar names and perhaps having similar results in some circumstances, are very different from each other. Nuclear fission is the process of splitting the nucleus of an atom, which normally has the effect of generating a large release of energy, such as is seen in nuclear bombs. Nuclear fission is also how most nuclear power plants generate energy.

Nuclear fusion as a source of manmade energy is still largely in the developmental stage, though some fusion power plants are online. While some energy from nuclear fusion is manmade, most of the energy coming from nuclear fusion that humans and other life forms benefit from comes from the sun. Nuclear fusion is the process by which all stars generate energy.

The problem with generating nuclear fusion lies in getting two atoms having the same charge close to each other. Atoms have the same charge generally repel each other, rather than being brought together. However, once brought together, nuclear force begins to take over. This force will attract the nuclei of two or more atoms toward each other and start nuclear fusion, but this happens only if they are of close enough proximity.

To get the nuclei close enough together to produce nuclear fusion requires finding some way to get the atoms close together. In most cases, this is accomplished with very high levels of heat. The heat causes the atoms to speed up, allowing them to overcome their electromagnetic tendencies to repel each other. Though this can require a great deal of energy, the energy that results is often much greater than the energy put into it. In some cases, the heat from the explosion can create ongoing nuclear fusion reactions. These are called self-sustaining reactions. Stars, as mentioned before, are a good example of a self-sustaining reaction.