The Tibetan Plateau is the broadest plateau in the world with an average elevation of about 4-5 km, which is still growing vertically and laterally. How such a broad and highly elevated plateau formed and persisted, however, is still not well understood. Two groups of models of deformation and growth of Tibet have been proposed: the first is the shortening and thickening model, and the second is the mid/lower crustal channel flow model. Seismic evidence can help to discriminate between these competing models. In this presentation, I will discuss the constraints on the growth model from our 3D seismic model of Tibetan crust. I will briefly introduce how I build the 3D crustal model and describe the main features of our 3D model. Then, I will discuss the origins of these seismic features and their implications for the deformation and growth of Tibet.