A new picture of the dynamics at the base of the Earth's mantle is emerging from the integrated work of seismologists, geodynamicists, and geomagnetists. The structure at the core-mantle boundary (CMB) appears to be influencing convective motions both in the solid silicate mantle and in the liquid-iron outer core. Such processes are apparently at work at the CMB beneath eastern Indonesia, where very slow seismic velocities suggest an unusually hot region and could signal the birth of a mantle plume. In addition, geomagnetic modeling indicates that rising plumes could exist here in the core, which could represent dynamic coupling between the mantle and core.