I work with seismologists and mineral physicists to understand the seismic anisotropy in Earth's lowermost mantle. Below is a snapshot from geodynamic modeling, in which we use tracers to track the deformation of slabs. The deformation information is latter fed into mineral physics models to calculate seismic anisotropy. We find that observations of radial anisotropy and splitting in subhorizontal phases are mostly consistent with our models of post-perovskite with (010)-slip and (001)-slip. Our model of (001)-slip predicts stronger splitting than for (010)-slip for horizontally propagating phases in all directions. The strongest seismic anisotropy in this model occurs where the slab impinges on the core-mantle boundary.