All electrons, nucleons, and other particles or quanta (because quantum mechanics is applied to all particles, these should be known as quanta) undergo a persistent spin motion without possessing any infinite energy source, and therefore, they should have a unique structure that maintains their spinning and provides all the properties that they display. Additionally, because nothing in nature occurs without a reason or purpose, there should be an explanation for their persistent spinning motion. The photons also possess spin motion that they derive from the orbiting electrons from which the photons are emitted, and not obtain from their unique structure. Therefore, purpose why all electrons, nucleons, and other particles possess persistent spin motion, and unique structures of electrons and nucleons have been determined. The results of the determination of the purpose why all electrons, nucleons, and other particles possess persistent spin motion provide very clear and complete explanations for all related phenomena. Present study is focused on to provide clear and complete understanding of the phenomena of interference and diffraction of electrons and photons.