The book describes the quantum-mechanical motion in the context of the quantum field theory. A relativistic particle requires time and length thresholds in order to move quantum-mechanically, as a consequence of its relativistic rest energy and momentum. The subject is discussed mainly in relation to the Dirac equation for the electron and the electromagnetic interaction. Electromagnetic quantum-mechanical effects are computed. Also, the book presents the theory of the electromagnetic field, the relativistic motion, especially the motion of a charge in the electromagnetic field, as well as the electromagnetic field in matter and the surface electromagnetism.