We describe here the humanoid challenge that is part of the RoboCup robot soccer competitions. We focus on how relevant research issues of humanoid robotics — for example, biped walking and human-like sensors and actuators — can be addressed, and we investigate how teams proceed to solve the given tasks. Thus, new technologies like artificial muscles and artificial skin might find their way into the competition very soon. We detail examples of these technologies and discuss in which way they may contribute to RoboCup, and in return how RoboCup may serve as a benchmark for achievements within these technologies. Further we describe how RoboCup works as an open, worldwide cooperative project in robotics and AI.