Crazyflie is an open-source and open-hardware nano quadcopter made by Bitcraze. There are two models available: Crazyflie 1 is the older discontinued version, weighing just 19g. Crazyflie 2.0 is the current model with more features but slightly heavier (27g).

Both are supported by ROS and can be controlled from a host computer using a special USB dongle called Crazyradio.