This book presents the first comprehensive exposition of the interpretation of quantum mechanics pioneered by Louis de Broglie and David Bohm. The purpose is to explain how quantum processes may be visualized without ambiguity or confusion in terms of a simple physical model. Dr. Holland develops the idea that a material system such as an electron is a particle guided by a surrounding quantum wave. He examines the classic phenomena of quantum theory in order to show how the spacetime orbits of an ensemble of particles can reproduce the statistical quantum predictions. The book will therefore appeal to all physicists with an interest in the foundations of their discipline.