In particle physics, preons are point particles, conceived of as sub-components of quarks and leptons. The word was coined by Jogesh Pati and Abdus Salam, in 1974. Interest in preon models peaked in the 1980s but has slowed, as the Standard Model of particle physics continues to describe physics mostly successfully, and no direct experimental evidence for lepton and quark compositeness has been found. Preons come in four varieties, plus, anti-plus, zero and anti-zero. W bosons have six preons, and quarks and leptons have only three. In the hadronic sector, some effects are considered anomalies within the Standard Model. For example, the proton spin puzzle, the EMC effect, the distributions of electric charges inside the nucleons, as found by Hofstadter in 1956, and the ad hoc CKM matrix elements. When the term "preon" was coined, it was primarily to explain the two families of spin- fermions: quarks and leptons. More recent preon models also account for spin-1 bosons, and are still called "preons". Each of the preon models postulates a set of fewer fundamental particles than those of the Standard Model, together with the rules governing how those fundamental particles combine and interact. Based on these rules, the preon models try to explain the Standard Model, often predicting small discrepancies with this model and generating new particles and certain phenomena, which do not belong to the Standard Model. Goals of preon models Preon research is motivated by the desire to: Reduce the large number of particles, many that differ only in charge, to a smaller number of more fundamental particles. For example, the electron and positron are identical except for charge, and preon research is motivated by explaining that electrons and positrons are composed of similar preons with the relevant difference accounting for charge. The hope is to reproduce the reductionist strategy that has worked for the periodic table of elements. Explain the three generations of fermions. Calculate parameters that are currently unexplained by the Standard Model, such as particle masses, electric charges, and color charges, and reduce the number of experimental input parameters required by the Standard Model. Provide reasons for the very large differences in energy-masses observed in supposedly fundamental particles, from the electron neutrino to the top quark. Provide alternative explanations for the electro-weak symmetry breaking without invoking a Higgs field, which in turn possibly needs a supersymmetry to correct the theoretical problems involved with the Higgs