The advent of digital technology and image processing in the 1970s has marked a new era of human machine interaction. Since then there has been a rapid development in the eye monitoring field – a sub-area of intelligent human computer interaction – that brought up efficient ways for computers to support and assist humans while engaging in non-trivial tasks. The p- pose of this book is to provide a comprehensive in-depth coverage of both theory and practice of Passive Eye Monitoring. Passive Eye Monitoring is the science of teaching computers to autom- ically determine, in digital video streams, the spatial location, pupil’s act- ity, 3D gaze direction, movements and closure state of an individual’s eye, in real-time. It gained a lot of attention as opposed to invasive eye monitoring techniques like Electro Oculography and Magnetic Search Coil. Thetheory and practice of passive eye monitoring have now reached a level of maturity where good results can be achieved for applications – in automotive, mi- tary, medicine, information security and retrieval, typing and reading, online search, marketing, augmented and virtual reality, and video games – that were certainly non realistic a few decades ago. For instance, this technology has the potential to allow a disabled person to compose electronic messages, browseand navigatethroughwebpages,interactwith consumer – electronics devices, and while steering an operating machine, this technology monitors his/her fatigue and distraction state and issues appropriate vigilance wa- ings.