Notable simplifications arise in QCD in the Regge limit, allowing for an all-order resummation of asymptotically dominant contributions to scattering amplitudes. Applications of high-energy factorization range from perturbative forward scattering to the description of initial stages of heavy ion collisions. Recent progress on the understanding of Lipatov´s effective action as an unified framework to describe all these phenomena, and connections to N=4 SYM theory, are discussed.