We present a summary of the physics of gluon saturation and non-linear QCD
evolution at small values of parton momentum fraction x in the proton and
nucleus in the context of recent experimental results at HERA and RHIC. The
rich physics potential of low-x studies at the LHC, especially in the forward
region, is discussed and some benchmark measurements in pp, pA and AA
collisions are introduced.Comment: Invited overview talk at the 2nd HERA-LHC Workshop (CERN) and 4th
International Conference on Quarks and Nuclear Physics (QNP06, Madrid). 7
pages, 13 figs. To appear in EPJ-