Abstract　 　　
  The circumgalactic medium, the baryonic gas distributed in the distant galactic halo, plays a vital role in regulating galaxy formation and evolution. I will discuss recent progress in observing the circumgalactic medium, as well as how these observations help address some fundamental problems in galaxy formation and evolution. I will also discuss its connection to the intergalactic medium at large scale, and the implications to the “missing baryons” problem.