  Galaxies are surrounded by extended atmospheres, which are often called the
circumgalactic medium (CGM) and are the least understood part of galactic
ecosystems. The CGM serves as a reservoir of both diffuse, metal-poor gas
accreted from the intergalactic medium, and metal-rich gas that is either
ejected from galaxies by energetic feedback or stripped from infalling
satellites. As such, the CGM is empirically multi-phased and complex in
dynamics. Significant progress has been made in the past decade or so in
observing the cosmic-ray/B-field, as well as various phases of the CGM. But
basic questions remain to be answered. First, what are the energy, mass, and
metal contents of the CGM? More specifically, how are they spatially
distributed and partitioned in the different components? Moreover, how are they
linked to properties of host galaxies and their global clustering and
intergalactic medium environments? Lastly, what are the origin, state, and
life-cycle of the CGM? This question explores the dynamics of the CGM. Here we
illustrate how these questions may be addressed with multi-wavelength
observations of the CGM.
