Modular self-reconfigurable robots consist of many modules that can move relative to each other, thereby changing the overall shape of the robot. Developments in micromachining and molecular-scale technologies can allow creating such robots with a large number of tiny modules. I will describe how multiagent systems provide a useful approach to robust control for these robots, particularly dealing with their different physical scales. Fairly simple rules for the modules allow the robot to reconfigure for various locomotion and object manipulation tasks. I will illustrate these behaviors through simulation experiments on modular robots currently under construction. As one example, see http://arxiv.org/abs/cs.RO/0006030