Matter shows its energy (E) as potential energy (Ep), sharing energy (Es) and kinetic excess energy (Ee): E = Ep + Es + Ee. Matter or a system shows its excess energy (Ee > 0) as a free particle; after releasing or transferring the excess energy (Ee = 0), it keeps the remaining energy - its energy limit (Ep + Es) - as a (part of a) unity. Matter or a system shows its sharing energy (Es) as weight (to its unity centre Wu), which can be standardized as mass (m or Mu): Es = Wu = Mu. Unity force (Fu = Es + Ee) is matter’s tendency to be unity, expressed as repelling while excess-energy releasing (Ee → 0) out of a unity, or attracting while energy sharing (Ee = 0) in a unity. The Big Bang created four kinds of base particles: proton (p), electron (e), neutrino (v), and photon (γ). The neutrino is an energy-sharing agent and tends to be in a proton unity (pv), where the proton is the unity centre. Absent from nuclear fusion, a hydrogen nucleus has only one proton unity (pv). In a nuclear fusion centre, the base unities (pv and eγ) are so dense and hot that their sharing energy is raised so high from their potential energy (Ep → Es), they become energy sharing (nuclear fusing).