There are many different designations of interactive objects for touch screens, e.g. markers, marker objects, fiducials or "tangible objects". They all denominate physical auxiliaries different in shape and size, we call them markers. They can be recognized by the touch screen. Various technologies exist on the market: Some markers use optical recognition and can simply be printed similar to QR codes. Others use an integrated specific technology or mechanism and are generally a bit bigger in size. The markers are mounted or glued for instance to the actual object as an auxiliary.