What occurred before nucleosynthesis began?

Before nucleosynthesis began, the universe was in a hot, dense state known as the Big Bang, which occurred approximately 13.8 billion years ago. Following the initial explosion, the universe rapidly expanded and cooled, allowing fundamental particles like protons, neutrons, and electrons to form. This primordial environment persisted for about three minutes, during which temperatures dropped sufficiently for nucleosynthesis to occur, leading to the formation of light elements such as hydrogen, helium, and small amounts of lithium.