The Harari–Shupe preon model (also known as rishon model, RM) is the earliest effort to develop a preon model to explain the phenomena appearing in the Standard Model (SM) of particle physics. It was first developed independently by Haim Harari and by Michael A. Shupe and later expanded by Harari and his then-student Nathan Seiberg. The model The model has two kinds of fundamental particles called rishons (which means "primary" in Hebrew). They are T ("Third" since it has an electric charge of + e, or Tohu which means "unformed" in Hebrew) and V ("Vanishes", since it is electrically neutral, or Vohu which means "void" in Hebrew). All leptons and all flavours of quarks are three-rishon ordered triplets. These groups of three rishons have spin-. They are as follows: TTT = positron (anti-electron); VVV = electron neutrino; TTV, TVT and VTT = three colours of up quarks; VVT, VTV and TVV = three colours of down antiquarks. Each rishon has a corresponding antiparticle. Hence: = electron; = electron antineutrino; , , = three colours of up antiquarks; , , = three colours of down quarks. The W+ boson = TTTVVV; The W− boson = . Note that: Matter and antimatter are equally abundant in nature in the RM. This still leaves open the question of why , , and TTV etc. are common whereas TTT, TVV, and etc. are rare. Higher generation leptons and quarks are presumed to be excited states of first generation leptons and quarks, but those states are not specified. The simple RM does not provide an explanation of the mass-spectrum of the leptons and quarks. Baryon number () and lepton number () are not conserved, but the quantity is conserved. A baryon number violating process (such as proton decay) in the model would be In the expanded Harari–Seiberg version the rishons possess color and hypercolor, explaining why the only composites are the observed quarks and leptons. Under certain assumptions, it is possible to show that the model allows exactly for three generations of quarks and leptons. Evidence Currently, there is no scientific evidence for the existence of substructure within quarks and leptons, but there is no profound reason why such a substructure may not be revealed at shorter distances. In 2008, Piotr Zenczykowski has derived the RM by starting from a non-relativistic O(6) phase space. Such model is based on fundamental principles and the structure of