The goal of grand unification (or, grand unified theories—GUTs) is to unify the strong, weak, and electromagnetic interactions and the quarks and leptons within the framework of a gauge field theory based upon a simple or semi-simple, non-Abelian symmetry group, e.g., SU(5), SO(10), E 6. Such theories make two startling predictions: new interactions that violate baryon number (B) and lepton number (L) and thereby lead to the instability of the proton, and the existence of stable, superheavy magnetic monopoles (in the form of topologically-stable configurations of gauge and Higgs fields). Both predictions have very significant cosmological consequences.