All matter making up the stars, our planet and life upon it came into existence 13.8 billion years ago as a result of the Big Bang. A millisecond after the Big Bang occurred, neutrons and protons formed and began to fuse into small atomic nuclei. This is known as the Big Bang Nucleosynthesis (BBN) era. During BBN, protons (hydrogen), the main building blocks of stars, combined with neutrons to form helium and other light elements. All of this happened within the first, approximately, 20 minutes of this new universe.