The ability to gather, interpret, and react to sensory information actively and purposively is central to intelligent behavior. Gregory Hager's work focuses on understanding the connections between perception and reasoning or action. In past work, Hager has made several contributions in the areas of sensor fusion and sensor planning. His current research interests lie in the direction of developing systems that utilize visual feedback. He and his research group have developed two interesting tools in this area: XVision, a portable realtime feature tracking system, and ServoMatic, a portable hand-eye coordination system. His current work focuses on understanding the dynamical properties of image sequences of complex, articulated objects with the goal of developing vision-based systems that are able to interact safely and naturally with human partners.