Quadcopters are a relatively new type of radio-controlled flying device, mostly for hobbyists. They are strong enough to lift a camera, which allows for amazing videos and photos. But this ability also makes them controversial.
"The night skyline of the Chinese city of Guangzhou lit up by a
spectacular show in which hundreds of drones took to the air. In putting
on the show, the city broke its own world record for the biggest number
of drones involved in one performance."