The lecture will present the problem of periodic homogenization for the classical
Leray-Lions operators in nonlinear PDE's. It will introduce the unfolding method and show
how it applies in the case of periodically oscillating Leray-Lions operators. It will then
state more general results concerning the case of domains which are periodically
perforated with both homogeneous Neumann and Dirichlet conditions on the boundary of the
holes.