Seismic tomography, also named Earth CT, uses the observational seismic data to invert for the deep structures in the Earth. Body-wave travel-time tomography is one of the most popular and robust methods; it has revealed clear Earth structures and promoted the development of Earth Sciences. The past decades are important for seismic tomography because of the rapid accumulation of the observational seismic data and the increasing computer power. New results have successfully revealed the cycles of the materials and geodynamics within the Earth, the structures and seismotectonics of large earthquakes. This review summarizes the developments and new achievements of body-wave tomography in the new century. In East and Southeast Asia, seismic tomography revealed the geometry and structures of the subducting slabs, which stagnate in the mantle transition zone under East Asia but penetrate into the lower mantle directly under Southeast Asia. Seismic anisotropy further constrains on the upper mantle flows above the slabs, which are characterized as mantle convection in the big mantle wedge in East Asia while complex mantle flow probably affected by the Tibetan Plateau in Southeast Asia. In the source regions of large earthquakes, significant velocity and structural heterogeneities were revealed. Continental earthquakes are found to be related to the low velocity zones that may indicate the important role of the fluids. By contrast, the interplate earthquakes are related to the high velocity anomalies on the megathrust zones, where seismic anisotropy reflects the stress field on the fault plane and so provide essential constrains on the seismotectonics. Finally, this review discusses some technical items in body-wave travel-time tomography and how it can improve the understanding of the internal evolution and dynamics of the Earth in the future.