Superconductivity and ferromagnetism were considered exclusive phenomena for many decades. Ever since Kamerlingh Onnes' discovery that strong magnetic fields will destroy superconductivity it had been assumed that the large internal, or Weiss field, in a ferromagnet would never permit the occurrence of superconductivity. In the case of the magnetic elements, chromium, manganese, iron, cobalt, and nickel, this point of view certainly seems justified, as none of them has as yet been shown to be superconducting. And yet, whenever two phenomena seem to exclude one another so entirely, it is frequently because similar, if not identical, mechanisms are responsible.