Conceptual fractal illustration of a heavy element, such as uranium, undergoing fission. In nuclear physics and nuclear chemistry, nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts. The fission process often produces free neutrons and photons (in the form of gamma rays), and releases a very large amount of energy even by the energetic standards of radioactive decay. Nuclear fission of heavy elements was discovered on 1938 by German Otto Hahn and Fritz Strassmann, and explained theoretically in 1939 by Lise Meitner and Otto Frisch. A fractal is a never-ending pattern. Fractals are infinitely complex mathematical patterns that are self-similar across different scales. They are created by repeating a simple process over and over in an ongoing feedback loop.