Elementary particles, also known as fundamental particles, are subatomic particles which cannot be broken down into further sub-structures. These particles are not made up of any other particles. Therefore, elementary particles can be visualized as the fundamental constituents of all substance (matter and antimatter). The fundamental fermions (leptons, quarks, antileptons, and antiquarks) are an important example of elementary particles. Another important example of an elementary particle is a boson (such as the gauge boson and the Higgs boson).
Protons and neutrons are known to contain up and down quarks. These quarks can be classified as elementary particles. For an electron in an atom (or a molecule), the charge, orbital, and spin can be separated (with the help of a wavefunction) into a holon, an orbiton, and a spinon. However, an isolated electron which is not orbiting a nucleus can be considered to be an elementary particle (since it is believed to be unsplittable).