  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.
