Figure 1: The fundamental fermions and force carrying bosons of the standard model. (a) All matter is made up of leptons and quarks, which are spin-$1/2$ fermions. There are three families of leptons and three families of quarks. (b) The interactions between the fundamental particles occur through the exchange of bosons: the photon for the electromagnetic force, $W^{+}$, $W^{-}$, and $Z^0$ for the weak force, and gluons for the strong force. (From Ref. [3].)