Methods of local helioseismology provide three-dimensional images of the solar interior, giving insight about the subsurface structure and dynamics of convective structures and magnetic regions. Local helioseismology largely owes its success and fast developement to the MDI data that have been collected by SOHO over over the last ten years. Here I discuss in some detail what we have learned about the evolution and the lifetime of the supergranulation pattern, the variation of the wave speed under active regions and sunspots, and the connections between flows and magnetic activity. Interpreting seismic measurements is a challenging aspect of local helioseismology. Future progress will come from improved models of the sensitivity of the observations to localized perturbations in the Sun, including the effect of strong magnetic fields.