Casimir, himself a famous physician, studied and worked with three great physicists of the twentieth century: Niels Bohr, Wolfgang Pauli and Paul Ehrenfest. In his autobiography, the brilliant theoretician lets the reader witness the revolution that led to quantum physics, whose influence on modern society turned out to be many times larger than the first atomic physicists could have imagined. Through his involvement in the technical-scientific and the business aspects of physics, through management positions at Philips Research Laboratory and as a member of the Board of Directors of Philips, Professor Casimir is the ideal person to place half a century of developments in physics within the context of important events in the world.