Applying quantum mechanics to many-particle systems is an active area of research. The popularity of using quantum trajectories as a computational tool has exploded over the last decade, finally bringing this methodology to the level of practical application. This book explores this powerful tool to efficiently solve both static and time-dependent systems across a large area of quantum mechanics. Many of the pioneers who have either developed the subject from its inception or have improved on the subject contribute to this volume. They offer their insights on Lagrangian and Eulerian methods as well as various mixed quantum-classical techniques, among other topics.