Magnetization induced second harmonic generation (MSHG) is a new nonlinear magneto-optical technique that combines interface sensitivity with huge magneto-optical effects. These effects are due to the simultaneous breaking of inversion symmetry (at interfaces) and time-reversal symmetry (by the magnetization). Because most magnetically ordered materials are centrosymmetric in their bulk form, MSHG is a particularly interesting probe to study the magnetization structure of the interfaces in magnetic multilayer systems. Using MSHG, we have found e.g. that the spin orientation at the interface of CoNi/Pt multilayers can be different from the bulk due to specific preparation conditions. Due to both very high magneto-optical contrast and interface sensitivity, fine details of magnetization reversal become visible with MSHG imaging that are not detectable by usual magneto-optics. MSHG also appears to be highly sensitive for the step induced anisotropy in magnetic thin films grown on vicinal surfaces. In addition, effects of interface annealing and oxidation can be observed in situ, which is of great importance for sensor multilayer structures. By using phase sensitive spectroscopic MSHG experiments, the spin-dependent interface density of states can be probed, as was recently demonstrated in a study on a Ni(110) surface. This is of great importance for the understanding of e.g. the spin dependent tunnel current in magnetic tunnel devices. Finally, the use of fs laser excitation allows the probing of ultra fast magnetization dynamics, using pump-probe techniques. Recent results of this will be discussed. Part of this work was supported by FOM, the TMR Network NOMOKE and INTAS 97-0705 (ERBFMRXCT960015) and INTAS 97-0705.