The exoplanet revolution that began three decades ago has drastically changed our knowledge of the extra-solar systems. Today, we face an extreme diversity and complexity of these systems that can only be understood through the intimate link that exists between the planets and their host stars. The understanding, characterization, and the detection of the exoplanets has to be made in close collaboration between stellar and planetary physicists. The purpose of the school and this book is to provide an update of our current knowledge in some selected research fields dedicated to the interplay between stars and planets. It aims to prepare scientists for a rich new decade for exoplanets with space missions like the upcoming PLATO and ARIEL and the new instruments on the VLT and the future ELT.