Man-machine interaction is the gateway providing access to functions and services, which, due to the ever increasing complexity of smart systems, threatens to become a bottleneck. This book therefore introduces not only advanced interfacing concepts, but also gives insight into the related theoretical background.This refers mainly to the realization of video-based multimodal interaction via gesture, mimics, and speech, but also to interacting with virtual object in virtual environments, cooperating with local or remote robots, and user assistance. While most publications in the field of human factors engineering focus on interface design, this book puts special emphasis on implementation aspects. To this end it is accompanied by software development environments for image processing, classification, and virtual environment implementation. In addition a test data base is included for gestures, head pose, facial expressions, full-body person recognition, and people tracking. These data are used for the examples throughout the book, but are also meant to encourage the reader to start experimentation on his own. Thus the book may serve as a self-contained introduction both for researchers and developers of man-machine interfaces. It may also be used for graduate-level university courses.