This practical reference provides you a comprehensive in-depth coverage of both theory and practice of cutting-edge Passive Eye (-Gaze) Monitoring technology. It describes and examines vision algorithms, Human Factors methodologies, and hardware build in eye-gaze monitoring systems designed for various real-world applications, along with practical issues, including performance on experimental subjects, real-time measurements, and user calibration, feedback and acceptance. It helps you to understand the motivations, activities, trends and directions of researchers and engineers in Intelligent Human Machine Interaction and Eye Tracking in today's market, and offers you a view of the future of this rapidly evolving technological area. The book offers you a detailed description of vision algorithms and core building-blocks of a video-based eye tracking system (parts I and II), including: automatic detection of human eyes in videos, modeling the eyes' structure and appearance, tracking of spatial eye coordinates, identifying pupil, iris, eyelids, and eye-corners locations, estimating, calibrating and tracking a person's gaze direction, as well as interpreting and reconstructing displayed worlds' images on the eye's cornea. Part III through VI of this book provide a detailed coverage of recent successful use of eye monitoring systems, either as an interaction input device or a reliable source of data, in advanced applications including automotive, military, medicine, information security and retrieval, typing and reading, online search, marketing, gaze-contingent displays, augmented and virtual reality, and video gaming. Part III is on ``Gaze-Based Interactions'' and contains three chapters. Part IV includes two chapters on applications of eye monitoring in military and security realms. Part V presents recent deployment of the technology in automotive and medicine. The last part is on "Eye Monitoring in Information Retrieval and Interface Design Assessment".