Around 2002 two german guys set the path for today's quadcopters. They built the X-UFO and developed the X-3D and X-3D-BL sensors [1], which for the first time

Around 2002 two german guys set the path for today's quadcopters. They built the X-UFO and developed the X-3D and X-3D-BL sensors [1], which for the first time enabled amazing control capabilities for the still rather unknown quadcopters [2]. This led to the first success stories and the market kind of jumped on the train. Media did it's job and here we are. Technology has advanced a lot since then [3, 4]. Better and smaller sensors and microprocessors. More sophisticated materials and design, production and marketing processes. This surely played a big role as well, now that consumer market UAVs and flying toys can be produced quite cheaply. Also various open source projects popped up and nowadays even beginners can build and program their own quadcopter and PID controller. As for helicopter vs. quadcopter - The latter is much simpler to fly, especially with autopilots and control units such as the X-3D or today's AscTec Trinity. Also safety for consumer products is an issue, where quadcopters with their embedded propellers have the bonus. And its omni-directional nature of movement yields more freedom and fun, especially as a toy. [1] http://www.asctec.de/en/ascending-technologies/company/ http://www.asctec.de/en/ascending-technologies/company/ [2] https://www.youtube.com/watch?v=Csti6mHZNF4 https://www.youtube.com/watch?v=Csti6mHZNF4 [3] https://www.youtube.com/watch?v=Us0BqJvsF9k https://www.youtube.com/watch?v=Us0BqJvsF9k [4] see ChuckMcM's comment