Abstract　 　　
　 Disk galaxies are the dynamic ecosystem of many species. I will review recent X-ray observations that reveal an otherwise hidden species and its energetic interplay with other components of such galaxies. I will focus on answering four questions: 1. How do X-ray properties vary among galaxies? 2. Does the X-ray emission trace the accretion or feedback of galaxies? 3. What is the nature of the X-ray emission? 4. How can one conduct an X-ray tomography of a galaxy? I will also discuss how ongoing/future radio and X-ray observations can further advance our understanding of the galaxy ecosystem.