The circumgalactic medium (CGM) plays a critical role in galaxy formation and evolution by mediating inflows and outflows. Recent years have seen significant progress in observations and understanding of the multiphase nature of the CGM. This talk will specifically focus on two phases: the hot phase with temperatures of log T >~ 6 and the photoionized cool phase at log T ~ 4, which have the most well-constrained physical conditions. I will also briefly talk about intriguing puzzles associated with the warm gas at log T~5. In addition, I will introduce ongoing missions in the near future to advance our understanding of the CGM.
