We present a survey of the nonlinear optical properties of mesoscopic and composite materials with particular emphasis on the photoinduced modifications of their spectral features that are related either to the electron or photon confinement. The impact of static magnetic fields is also analyzed. These modifications reveal important aspects of the electrons spins and photons in confined spaces and can be exploited in different ways for optoelectronic and physicochemical applications as well. ©2001 American Institute of Physics.