In this Talk, I describe the most recent progress in the field of iron-based superconductors. Using neutron scattering as a probe, we study the spin wave excitations in BaFe2As2 and its electron/hole doping evolution of the spin excitations. The electronic nematic phase appears for both the parent and electron-doped superconductors, and has no relationship with orthorhombic structure. We also compare the evolution of high-energy spin excitations in FeAs superconductors with those of the copper oxides.