This dominant cosmological theory suggests the Universe began nearly 13.7 billion years ago, expanding rapidly from a very dense and incredibly hot state. Eventually, stars ignited and galaxies slowly formed. The Big Bang theory has been imporved and advanced especially through NASA's Cosmic Background Explorer (COBE) and WMAP missions. This animation conceptualizes these explosive beginnings of the Universe. Note: This animation begins with a pinpoint of light as the Big Bang, and continues to show the formation of the first stars and galaxies. Animator: Dana Berry (Skyworks Digital). Writer: Michael D. McClare (HTSI).