A bar magnet can be considered a dipole with a north pole at one end south pole at the other. A magnetic field can be measured leaving the dipole at the north pole and returning the magnet at the south pole. If a magnet is cut in two, two magnets or dipoles are created out of one. This sectioning and creation of dipoles can continue to the atomic level. Therefor, the source of magnetism lies in the basic building block of all matter...the atom.