Face recognition is one of the most important abilities that we use in our daily lives. There are several reasons for the growing interest in automated face recognition, including rising concerns for public security, the need for identity verification for physical and logical access, and the need for face analysis and modeling techniques in multimedia data management and digital entertainment. Research in automatic face recognition started in the 1960s. Recent years have seen significant progress in this area and a number of face recognition and modeling systems have been developed and deployed. However, accurate and robust face recognition still offers a number of challenges to computer vision and pattern recognition researchers, especially under unconstrained environments.