  We briefly review the recently constructed two orbital microscopic model for
iron-based superconductors based on $S_4$ symmetry (PRX 2 021009(2012)). With
this faithful representation of the kinematics of the tri-layer FeAs or FeSe
structure, the model provides answers and physical pictures to fundamental
questions related to the robustness of superconductivity and pairing symmetry,
unifies different families of iron-based superconductors, casts new insight
into the connections to the other high $T_c$ superconductors, cuprates, and
reveals why an s-wave pairing can be stabilized by repulsive interactions.
Further progresses include that the model provides a clean understanding of
band reconstruction observed in magnetically ordered states, which is a strong
support to the kinematics of the $S_4$ model, and captures the essential low
energy physics of iron-based superconductors based on numerical results from
unbiased quantum Monte Carlo simulation.
