High temperature superconductivity in the iron-based systems has commanded much attention since its discovery six years ago. There is by now an emerging consensus that electron correlations play an essential role in these materials.  The importance of the correlation effects was implicated from early on by the bad-metal behavior of the iron pnictides. It has been further highlighted by the observation of an antiferromagnetic insulator state in the overall phase diagram of the iron chalcogenides.

In this talk, I will address these and related aspects of the microscopic physics in the iron-based superconductors. Particular attention will be paid to quantum criticality and orbital-selective Mott physics. The connection of these properties with the magnetism and superconductivity will be discussed.