Distributed systems of multiple robots, called swarm robotics, are more robust than centralized systems consisting of single robots. The failure of one robot of a group need not prevent the others from performing a task. Furthermore, a group of collaborating robots can perform tasks that a single robot cannot. Swarm robotics is inspired by the behavior of colonies of insects such as ants and bees. Communications among the robots of a group can be direct, indirect (for example, by leaving markings) or physical. The BeeClust algorithm causes robots to cluster at areas of high sensor values by detecting collisions among them. The stick pulling algorithm demonstrates how two robots can collaborate to perform a task that neither could do alone. Occlusion-based pushing shows that a group of robots can collaborate even without explicit communications.