"... Before the year 1928, every physicist knew what we meant by an elementary particle. The electron and the proton were the obvious examples, and at that time we would have liked simply to take them as point charges, infinitely small, defined simply by their charge and their mass. We had to agree reluctantly that they must have a radius, since their electromagnetic energy had to be finite. We did not like the idea that such objects should have properties like a radius, but still we were happy that at least they seemed to be completely symmetrical, like a sphere. But then the discovery of electron spin changed this picture considerably. The electron was not symmetrical. It had an axis, and this result emphasized that perhaps such particles have more than one property, and that they are not simple, not so elementary as we had thought before."