Knowledge of linear inversion and exploration seismology is helpful. Consent of instructor is required.Overview of non-linear seismic inversion methods that invert for earth parameters from seismic data. The inversion procedure is a multiscale iterative method (typically, non-linear conjugate gradient) that employs preconditioning and regularization. Solution sensitivity is analyzed by model covariance matrices, the slice-projection theorem, and the generalized Radon transform. Methods for waveform inversion, wave path traveltime tomography, and least squares migration are presented.