I will demonstrate the rich physics we can learn from X-ray astronomy by highlighting two astrophysical systems with dramatically different size scales. On a large scale of a mega parsec (1 parsec = 3.26 light years), the X-ray emitting hot intracluster medium (ICM) of galaxy clusters is shock heated by the accretion of infalling materials. I will present theoretical models and the predicted X-ray signatures of the non- equilibrium ICM including electron-ion non-equipartition and non- equilibrium ionization (NEI) physics. On a small scale close to the accretion radius of the M87 supermassive black hole (~100 parsec), hard X-ray emission above 10 keV from its unresolved X-ray core has been detected, for the first time, with the NuSTAR X-ray Observatory. I will discuss our observational findings along with the origin of the X-ray emission, which is more likely to come from its relativistic jet rather than the accretion flow.