We introduce a formalism suitable to study hadronic collisions in the high-energy limit in quantum chromodynamics (QCD), and the transition to the saturation regime. In this framework, we rederive known results that are needed to present our personal contributions and we compute different cross-sections in the context of hard diffraction and particle production. We study the transition to the saturation regime as given by the BK equation, in particular we derive properties of its solutions. We apply our results to deep inelastic scattering and show that, in the energy range of the HERA collider, the predictions of high-energy QCD are in good agreement with the data. We also consider jet production in hadronic collisions and discuss the possibility to test saturation at the LHC.
