Physical properties, transition metal doping and phase diagrams in 122 and related iron pnictide superconductors. Is there a unified picture?

A brief overview of the interplay between magnetism, structure and superconductivity in $BaFe_2As_2$ and related compounds will be presented, with examples of different ``knobs" (or perturbations) that allow us to change the physical properties of these materials and with a discussion of empirical rules. The 122 materials will be contrasted to the recently discovered $K_xFe_{2-y}Se_2$ and related compounds.