Autonomous aerial systems have recently been at the forefront of robotics research, and currently enjoy a continuously expanding range of applications wherein they are actively utilized. Commonly these are called drones, but this survey of the current state-of-the-art also considers "Micro Aerial Vehicles" in order to emphasize the increasingly advanced levels of autonomy and the small scale of such systems. This monograph provides researchers, engineers and students with a comprehensive overview of core modeling, control, estimation, and planning concepts and approaches for micro aerial robots of the rotorcraft class. A comprehensive description of a set of methods that enable automated flight control, state estimation in GPS-denied environments, as well as path planning techniques for autonomous exploration is also provided, and serves as a holistic point of reference for those interested in the field of unmanned aerial systems. This monograph will be a valuable starting point for researchers and developers working in the exciting area of aerial robots of the rotorcraft class, or drones.