The collective and cooperation behaviour of living beings, such as flocks of bird, shoals of fish, herds of wildebeest has certain advantages, including avoiding predators, increasing the chance of finding food, saving energy. This book introduces how to build a robot flocking system with similar behaviour to biological flocking. You can learn how to control the robots to move like a group, cohesively avoid obstacles and cooperatively track a target. The flocking system is analysed with control theory and tested via realistic simulations and real robots experiments. You will see a group of wifibots using wifi-cameras to track a moving target and sixty UAVs flying like a swarm.