The model-making sector of multicopters is very young. It started at the beginning of the new millennium with commercial products for flying camera inspections. Hobby users were able to fly their first systems in 2005, when the first toy companies launched relatively inexpensive toys with four propellers arranged horizontally. It was not until today's microprocessor technology, which can evaluate sensors for position stabilisation and change the speeds of the motors accordingly, that this fascinating subject became accessible for model building. This book is intended to help understand the functional principle, the motors, sensors, and control systems used and, on the other hand, to give an overview of what can be done today with this technology. Compared to the previous book, much new and updated information has been added and the ready-made systems that can be bought today are also discussed.