  These are introductory lectures to some aspects of the physics of strongly
correlated electron systems. I first explain the main reasons for strong
correlations in several classes of materials. The basic principles of dynamical
mean-field theory (DMFT) are then briefly reviewed. I emphasize the formal
analogies with classical mean-field theory and density functional theory,
through the construction of free-energy functionals of a local observable. I
review the application of DMFT to the Mott transition, and compare to recent
spectroscopy and transport experiments. The key role of the quasiparticle
coherence scale, and of transfers of spectral weight between low- and
intermediate or high energies is emphasized. Above this scale, correlated
metals enter an incoherent regime with unusual transport properties. The recent
combinations of DMFT with electronic structure methods are also discussed, and
illustrated by some applications to transition metal oxides and f-electron
materials.
