Quantum electrodynamics — or QED, for short — is the revolutionary theory that explains how light and electrons interact. Thanks to Richard Feynman and his colleagues, who won the Nobel Prize for their ground-breaking work in this area, it is also one of the rare parts of physics that is known for sure, a theory that has stood the text of time. Based on a series of lectures delivered to the general public at the University of California, Feynman here wittily explains the theory of quantum electrodynamics, the central aspect of much of modern physics.