Teller suggested that we... we put our attention to a more difficult problem, because after all it was obvious one could make a uranium or plutonium bomb, and so one should now see how to go on from there. And in a conversation with Fermi, Teller had been stimulated to the idea that once you had an atomic explosion you would develop very high temperature and that high temperature would be enough to... to initiate nuclear reactions between light nuclei; just like there are in the stars. And so most of the time of this study group in Berkeley was devoted to studying what we called the 'Super', that is the device in which deuterium would be initiated and would be set to react and you would get a big cylinder of deuterium to explode. The energy set free per unit mass in deuterium is much bigger than it is in uranium or plutonium, and also it was... it seemed that this was an unlimited possibility. Well, we soon found that it wasn't all that easy, first there were troubles from the fact that you would excite a lot of radiation and that radiation would then keep the temperature low. And, after many, many years, by 1949, it was pretty clear that indeed this scheme would not work, but it was our main... main idea at the time.