This course presents the fundamental aspects of modern flow control. The framework of the course will be cast starting with a brief review of the development of flow control from its birth at the turn of the 20th century to current state of the art techniques and methodologies. The key concepts, fundamental to modern flow control, will thus be extracted and categorized throughout the course; including topics such as flow instabilities; dynamic and closed-loop control; actuators and sensors; modeling and simulations.