The r-process ("r" for "rapid'") is the creation of elements heavier than zinc through the intense bombardment of other elements by neutrons. It occurs on a timescale so short compared to the time needed for nuclear decay via the emission of a beta particle that it enables chains of reactions involving highly unstable intermediate nuclei to take place. It is believed to occur in supernovae, which unleash a fierce flux of neutrons, and to be responsible for the manufacture of most of the elements in the periodic table more massive than iron.