First three minutes. Artwork of a timeline of events after the Big Bang up to the first three minutes. The elementary particles are electrons (dark blue), light photons (squiggles), up quarks (yellow), and down quarks (blue). Neutrinos and other quarks are not shown. Minus signs indicate anti-matter particles. The curved lines (white) indicate time elapsed since the Big Bang. A tiny fraction of a second after the Big Bang, the universe emerged from the inflation era (top left corner) and entered the particle era (upper left). At one second, the quarks began to combine in groups of three to form protons (2 down quarks, 1 up quark) and neutrons (1 down quark, 2 up quarks) in the nucleosynthesis era (centre). After three minutes, in the nuclei era (right), protons and neutrons combined to form atomic nuclei (hydrogen, deuterium, helium, lithium).