I think that where we first knew it was when we were trying to identify the atomic number of the next two elements, those with the atomic number 95 and 96 — remember neptunium was 93, plutonium was 94 — and were not succeeding. Then I got this idea of the actinide concept. We applied those new chemical concepts then, and then we began to detect the isotopes of the next two elements. That was a moment of excitement. That was probably one of the most exciting moments of my life.