The activity of stars such as the Sun modulates the environment within their astrospheres. This variable forcing is mediated via stellar magnetic fields, radiative and energetic particulate flux, stellar winds and magnetic storms. In turn this influences planetary atmospheres, climate and habitability. Studies of this intimate relationship between the parent star, its astrophere and the planets that it hosts have reached a certain level of maturity within our own solar system – fueled both by advances in theoretical modelling and a host of satellites that observe the Sun-Earth system. Based on this understanding the first attempts are being made to understand Star-Planet interactions and their coupled evolution, which have relevance for habitability and the search for habitable planets in other stellar environments. This symposium will bring together scientists from diverse, interdisciplinary areas such as solar, stellar and planetary physics, atmospheric and climate physics and astobiology to review the current state of our understanding of solar and stellar environments, fertilize exchange of ideas and identify outstanding issues whose understanding necessitates coordinated scientific efforts.