Eight different massless force carriers called gluons exert the force that holds quarks together. Gluons are members of the boson family. Bosons have integral spin while quarks, electrons, and neutrinos have half-integral spins and are called fermions. Bosons can be created or destroyed while fermions can be created only if an antifermion is also created. A single fermion cannot be destroyed unless an anti-fermion is simultaneously destroyed.