Advances in experimental techniques are allowing researchers to investigate the extremes of the dynamics of particle interactions with electromagnetic fields. The theoretical tools at our disposal are classical and quantum mechanics and experience has shown that it is dangerous to dismiss one at the expense of the other. Each has merits that should be fully explored; the problem, however, is to bridge the gap between them so that the information they give is complementary rather than contradictory. In this book, that goal is achieved by formulating five postulates, and the level of their...