Activity of cool dwarf stars can reveal itself in the form of high-energy radiation (eg, enhanced X-ray coronal emission, flares) and particles (eg, winds, coronal mass ejections). Together, these phenomena shape the space weather around (exo)planets. Because most of the known exoplanets have significantly closer orbital distances than solar system planets, they are often embedded in much harsher particle and radiation environments, leading to stronger interactions between the exoplanet and its surrounding environment. In this talk I will present an overview of how stellar activity and outflows can induce and shape atmospheric escape in exoplanets. I will focus mostly on close-in gas giant planets, whose escaping atmospheres are somewhat easier to observe. I will then discuss how the observability of atmospheric escape, through spectroscopic transits, evolve on billions of years timescales.