In order to ensure a pedagogical presentation of the fundamentals, this book, which is based on 45 years of experience, endeavors to identify the main principles of the control scheme and its dynamics. The control loop is extensively developed because of the reference it constitutes in control. By establishing the control loop as equivalent to any other control or, more precisely, by making an elementary control loop appear, it becomes possible to reveal a part of this loop in other controls and, thanks to its regulator, qualitatively evaluate the control strategy. A comparative analysis then shows that the complexification of the control scheme does not necessarily go hand in hand with a better control strategy and therefore a better performance. Since robustness results from innovations in terms of performance desensitization, the CRONE control is presented, in view of the genuine domains of uncertainty taken into account and the small number of parameters to be optimized. The educational nature of this book is enhanced by numerous solved problems that develop examples of synthesis of different controls. Control in System Dynamics is intended for a very wide audience, including engineers, researchers, teachers and students hoping to expand their knowledge of control and dynamics in automatic control.