Hadron and Lepton Epochs

Before these eras, the early Universe was dominated by quark-gluon plasma. Th first of the two, the Hadron epoch, began .000001 seconds after the Big Bang. In this epoch, quarks became stable enough to bind together and form hadrons such as protons and neutrons. At 1 second after the Big Bang most hadrons and anti-hadrons annihilated each other leaving a residue that would later form atomic nuclei in a process called Big Bang Nucleosynthesis. The lepton epoch lasted from 1 to 3 seconds after the Big Bang. In that time leptons, including electrons, and anti-leptons were formed. At the end of the epoch, these pairs were annihilated as well, leaving another small residue. After these epochs the Universe was dominated by photons until about 380,000 years after the Big Bang.