early universe

The term early universe is used to refer to the universe from the Big Bang through some of its early phases. Early stages include inflation, the synthesis of protons and neutrons (both taking place well within the first second), and Big Bang nucleosynthesis (within the first few minutes). The phrase may refer to just such very early stages, or alternately may refer to its history through recombination (about 377,000 years after the Big Bang), or even through the epoch of reionization (millions to a billion additional years).