This interest in the practical application of science is frequently misunderstood as the trivial attempt of the scientist to acquire economic wealth, to earn money. It is true that this trivial motive does play a role sometimes, depending of course on the individual people. But it should not be overestimated. There is another much stronger motive which fascinates the good scientist in connection with practical application, namely: to see that it works; to see that one has correctly understood nature. I remember a conversation with Enrico Fermi after the war, a short time before the first hydrogen bomb was to be tested in the Pacific. We discussed this plan and I suggested that one should perhaps abstain from such a test, considering the biological and political consequences. Fermi replied, “But it is such a beautiful experiment.” This is probably the strongest motive behind the applications of science; the scientist needs the confirmation from an impartial judge, from nature herself, that he has understood her structure. And he wants to see the effect of his effort.