In cosmology, eternal inflation is a prediction of some forms of the model of cosmic inflation, a theory developed to explain issues in the original Big Bang theory. According to eternal inflation, the decay of the meta-stable false vacuum in one region led to the inflationary phase of the universe's expansion. In surrounding regions, the false vacuum continues to expand and decay can occur in surrounding regions, resulting in other universes inaccessibly distant from ours. This process lasts forever. Eternal inflation, therefore, produces a hypothetically infinite multiverse, in which only an insignificant fractal volume ends inflation.