Earth’s mantle and crust as we see them today are the result of the dynamic behaviour and evolution of our planet. Interaction between mantle and crust occurring along plate boundaries as well as in intra-plate settings shaped the (isotope) geochemical composition and diversity of both reservoirs. Research projects in this theme investigate material transfer happening on relatively short time-scales within subduction zones and the incorporation of crustal material on a much longer time-scale in plume-related magmatism. The application of non-traditional isotope signatures like Cr, Fe, Zn and Mo offer exciting new insights into processes taking place in the deep Earth as for example partial melting and melt-rock interaction. Combination with radiogenic systems offers additional understanding of the timeline of the investigated processes.