Define Nucleosynthesis and describe what it was like in the first few minutes after the Big Bang

Actually, in physical cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than H-1, the normal, light hydrogen, during the early phases of the universe, shortly after the Big Bang. About first millisecond, the universe had cooled to a few trillion kelvins (1012 K) and quarks finally had the opportunity to bind together into free protons and neutrons. Free neutrons are unstable with a half-life of about ten minutes (614.8 s) and formed in much smaller numbers. The abundance ratio was about seven protons for every neutron. Before one neutron half-life passed nearly every neutron had paired up with a proton, and nearly every one of these pairs had paired up to form helium. By this time the universe had cooled to a few billion kelvins (109 K) and the rate of nucleosynthesis had slowed down significantly.