Dy2Ti2O7: This rare, "spin ice", crystal contains the atomic monopoles needed to create magnetricity. via Muon Science Laboratory
In 1931, physicist Paul Dirac hypothesized that on the quantum level, magnetic charge must exist in discrete packets, or quanta, in the same way that electric energy exists in a photon. This implies the existence of magnetic monopoles: particles that have a single magnetic charge, or polar identity -- north or south.
For 78 years, Dirac's speculation interested only hardcore theorists, because the conjecture failed to find any expression in observed phenomena. All magnets had two poles, one north and one south, inextricably attached to each other.