Marc’s work has a strong interdisciplinary background. He combines methods and approaches from artificial intelligence, real-time interactive systems, 3D graphics, cognitive sciences, and psychology on top of a strong engineering foundation in computer science. Since his seminal work on multimodal–gesture and speech–interaction in Virtual Reality from the late 90th, he is interested in highly interactive and immersive interfaces of Virtual, Augmented, and Mixed Reality (VR, AR, MR). Current research topics focus on embodiment, i.e., of avatars and agents, body ownership and the Proteus effect, time perception, social VR, multimodal input/output, gamification, technical characteristics of, and engineering solutions for VR/AR, and application areas for therapy (e.g., of neurological deficits or obesity disorders), training, learning, and entertainment.