How galaxies get their gas and how much mass, energy, and metals galaxies return to their surroundings are questions central to our understanding of galaxies and the intergalactic medium. Only stars synthesize metals, yet only about half of the generated elements are found in stars and the interstellar medium. Galaxies are also missing their share of baryonic matter. Understanding the flows of the matter/energy in and around galaxies, or their "ecosystem'', is the focus of my research. A key to the understanding of the matter and energy flows is the study of various high-energy feedback processes in galaxies. I have concentrated on four closely-related aspects of this research topic: examining various high-energy sources of the interstellar medium (e.g., supernova remnants, superbubbles, and galactic nuclear regions, including the accretion process around black holes);characterizing the global structure as well as the physical and chemical states of hot gas in and around galaxies; investigating the interplay of high-energy radiation and gas with other galactic components; exploring the interaction of galaxies with their environment, particularly the intragroup/cluster media. I primarily uses radio, infrared, ultraviolet, and X-ray observations to conduct these studies. I also carry out theoretical and computational studies with my students and collaborators.