In 1915, H.A. Lorentz published his works with the same title. I am not trying to plagiarize but to post the questions: Is an electron a point or composite particle? Can the electron be shown to have a substructure? The answer is "yes" to both questions. The hypothesis that is responsible for these answers is that all particles (fermions and bosons) are all composites. If we theorize that there are two kinds of mass: the potential mass (H-) and the kinetic mass (H+), then all particles are composites of potential mass and kinetic mass. A particle is a fermion if there are odd number of potential and odd number of kinetic mass in it. If these are even, then it is a boson. The actual detectable experimental mass of the particle come about when the the number of p-mass and k-mass of each particle are not the same. This is an alternative explanation for the mass of the W's and Z's particles in the electroweak theory which are k-mass.