In the past several years, there have been many important developments in the rapidly emerging field of atom interferometry. Atom interferometers have been constructed by several research groups around the world and used both as inertial sensors and for precision measurements. Also, atom interferometers allow researchers to probe interesting fundamental questions in quantum mechanics. This volume contains contributions from theoretical and experimental physicists at the forefront of these developments. There is a balance of background material and recent results that will enable the reader to acquire both a general overview of atom interferometry and an appreciation of the promise it holds for the future.