C. N. Yang:We have just heard three speakers describing to us various problems which arise in theoretical and experimental high‐energy physics, and in the designs of high‐energy accelerators. The problem of the aims, prospects, and the impact of the whole enterprise is a very complex subject. I shall confine myself to a few remarks concerning the historical aspect of the subject. High‐energy physics is a natural continuation of the traditional efforts by physicists to study the structure of matter. By all standards of comparison, I think we are not exaggerating when we say that achievements in this line of research have been most spectacular in the past sixty years. At the turn of the century, physicists, as we recall, were just looking at the structure of atoms. Thirty years later, the subject of studies progressed to atomic nuclei, and today we are looking at subnuclear constituents. The increase in energy is equally impressive; in fact, perhaps even more so. We have progressed from a few electron volts to millions of electron volts to today's multibillion electron volts. Reviewing the progress of the experimental techniques that have made possible these investigations, one is deeply impressed by the power and the ingenuity that were brought to bear at each stage of this development. With the greatly awakened interest in science in all nations, with the rapid progress of technology, there seems to be little doubt that new experimental techniques will be developed to meet every new challenge encountered in this enterprise. The impact of these developments on technology, on human affairs, and on other sciences has been important beyond description.