3D transdimensional seismic tomography of the inner core

•The inner core of the Earth exhibits seismic anisotropy and lateral heterogeneity.•We use a large body wave dataset with a transdimensional MCMC methodology to solve for inner core anisotropic velocity in 3D.•We resolve a anisotropic western zone primarily isolated in the northern hemisphere.•An innermost inner core with anomalous anisotropy located in the east and an isotropic outer inner core.•This has implications for models of inner core growth and possibly indicated different phases of iron in the inner core.