Light dynamical fermions on the lattice: toward the chiral regime of QCD

Algorithmic and technical progress achieved over the last few years makes QCD simulations with light dynamical quarks much faster than before. As a result lattices with pions as light as 250–300 MeV can be simulated with the present generation of computers. I review recent conceptual and numerical progress in this field, with particular emphasis on results obtained and difficulties encountered in simulations with significantly smaller quark masses with respect to previous computations. I also attempt to compare physical results for pion masses and decay constants available to date in the two-flavour theory with expectations from chiral perturbation theory.