Biometric recognition, or simply Biometrics, is a rapidly evolving field with applications ranging from accessing one's computer to gaining entry into a country. Biometric systems rely on the use of physical or behavioral traits, such as fingerprints, face, voice and hand geometry, to establish the identity of an individual. The deployment of large-scale biometric systems in both commercial (e.g., grocery stores, amusement parks, airports) and government (e.g., US-VISIT) applications has served to increase the public's awareness of this technology. This rapid growth has also highlighted the challenges associated with designing and deploying biometric systems. Indeed, the problem of biometric recognition is a "Grand Challenge" in its own right. The past five years has seen a significant growth in biometric research resulting in the development of innovative sensors, robust and efficient algorithms for feature extraction and matching, enhanced test methodologies and novel applications. These advances have resulted in robust, accurate, secure and cost effective biometric systems. The Handbook of Biometrics -- an edited volume contributed by prominent invited researchers in Biometrics -- describes the fundamentals as well as the latest advancements in the burgeoning field of biometrics. It is designed for professionals composed of practitioners and researchers in Biometrics, Pattern Recognition and Computer Security. The Handbook of Biometrics can be used as a primary textbook for an undergraduate biometrics class. This book is also suitable as a secondary textbook or reference for advanced-level students in computer science.