ATHENA (Advanced Telescope for High-Energy Astrophysics) is an X-ray mission selected by ESA within its Cosmic Vision Program to address the Hot and Energetic Universe scientific theme. The outstanding capabilities of Athena as an observatory are expected to make a profound impact in essentially all fields of Astrophysics, from understanding the structure and energetics of stellar winds to probing the physics of the enrichment and heating of our Galaxy's Inter-stellar Medium by supernova explosions.