  It has been recently understood how to deal with high-energy scattering
beyond the mean field approximation. We review some of the main steps of this
theoretical progress, like the role of Lorentz invariance and unitarity
requirements, the importance of discreteness and fluctuations of gluon numbers
(Pomeron loops), the high-energy QCD/statistical physics correspondence and the
consequences for the saturation scale, the scattering amplitude and other, also
measurable, quantities.
