At 10-10 s during the evolution of the universe, formed, which are elementary particles that make up protons and neutrons.

The protons and neutrons are bound together to form the primordial atomic nuclei of simple elements: hydrogen and helium 4, small amounts of deuterium, helium 3 and lithium 7. It takes another 300,000 years for electrons to capture into orbits around nuclei to form constant atoms.