We discuss nanoclusters of titanium dioxide, bulk CdTe and CS 2 as characteristic materials to illustrate two main ideas; firstly, it is possible to argue about the origin of the nonlinearity even with a high repetition laser, provided that you have as large a peak power (50 kW) as the one found in femtosecond lasers. Secondly, the search for dimensional confinement to enhance nonlinear optical properties has experienced some difficulties with conflicting results. We show that electronic nonlinear behavior increases from TiO 2 , CS 2 to CdTe and the nonlinear thermal effect increases from CS 2 , CdTe to TiO 2 .