Lepton Epoch

With most hadrons formed, the universe is dominated by leptons, especially electrons and neutrinos. These lightweight particles carry much of the remaining energy and interact frequently with radiation.

Protons and neutrons persist, but cannot yet combine into larger nuclei. Conditions remain too hot and energetic for stable nuclear binding beyond the simplest forms.

As the universe expands further, neutrinos decouple and stream freely through space. Matter continues to simplify, preparing the conditions for nuclear formation.