Quantum mechanical particles are classified as bosons or fermions. Fermions have half-integer spin; for all known elementary fermions this is . All elementary particles are either bosons or fermions. All observed elementary particles are either fermions or bosons. Dirac particles which behave like massless relativistic fermions have been observed in 3D topological insulators. A Dirac fermion is equivalent to two Weyl fermions. One distinguishes bosons (integer spin) and fermions (half-integer spin). Creation/annihilation operators are different for bosons (integer spin) and fermions (half-integer spin). Einstein statistics, each applicable to a different class of particles, fermions and bosons. Quarks are particles of spin-, implying that they are fermions. The Standard Model recognizes two types of elementary fermions&colon; quarks and leptons. It is analogous to the original description of SUSY, which referred to bosons and fermions. Even without transfer, graphene on SiC exhibits massless Dirac fermions. Technicolor avoids this problem by hypothesizing a new gauge interaction coupled to new massless fermions. Leptons are particles of spin-, meaning that they are fermions.