  Stars over a wide range of masses and evolutionary stages are nowadays known
to emit X-rays. This X-ray emission is a unique probe of the most energetic
phenomena occurring in the circumstellar environment of these stars, and
provides precious insight on magnetic phenomena or hydrodynamic shocks. Owing
to its large collecting area, Athena+ will open up an entirely new window on
these phenomena. Indeed, Athena+ will not only allow us to study many more
objects with an unprecedented spectral resolution, but will also pioneer the
study of the dynamics of these objects via time-resolved high-resolution
spectroscopy. In this way, Athena+ will be a unique tool to study accretion
processes in TTauri stars, flaring activity in young stars, dynamos in
ultra-cool dwarfs, small and large-scale structures in the winds of single
massive stars, wind interactions in massive binary systems, hot bubbles in
planetary nebula... All these studies will lead to a deeper understanding of
yet poorly understood processes which have profound impact in star and
planetary system formation as well as in feedback processes on Galactic scale.
