Stars and their exoplanets evolve together over billions of years, just like our own solar system. Many known exoplanetary systems have planets orbiting their host stars at much closer distances than we observe in the solar system, with orbital periods of only a few days. In such systems one expects the star and its close-in planet to interact through tidal and magnetic forces, tying their evolution together. These interactions can give us insights into fundamental properties of star- planet systems which are hard to constrain otherwise: the time scale over which close-in planets spiral into the star, the evolution of stellar activity, and the amount of atmospheric evaporation and the habitability for all planets in a system with a close-in planet. Gaia and other telescopes have now opened up new pathways to measure how stars and planets interact with each other. I will present new approaches to test for planet-induced influences on stars through wide binary systems, motivate a new look at stellar magnetic activity measurements, and discuss how planetary atmospheres can evaporate over the lifetime of exoplanets.