The lowermost mantle is a mysterious region that has enormous potential to shed light on the process of core-mantle interaction, subducting slabs, and the large-scale mantle convection. The extreme heterogeneity recently observed at this region plus their mineral and dynamical interpretations may provide some important clues to Earth's early evolutionary history. This session is going to collect and summarize the most recent advances in multidisciplinary fields regarding the new understanding of Earth's lowermost mantle.