We are organizing a session focusing on 'Water in the deep Earth' at the European Mineralogical Conference that will be held in Dublin (Ireland) *18-23 August 2024 * *Session title:* Water in the deep (and not so deep) Earth *Deadline for Abstract submission*: 22 March, 2024 *Session description:* Water and its derived species (H+, OH-, H2) are major players in controlling the genesis of magma, as well as its mobility, viscosity and eruptivity. At the atomic scale, water/hydrogen also impacts the viscosity of mantle rocks and minerals, in addition to affecting their electrical conductivity, ionic diffusivities or seismic properties, and thus geodynamics. In crustal domains, water/hydrogen is also a key actor of oceanic crust, impacting the dynamics of subduction, as well as the thermal profile and redox state of the down-going slab. Continental crust, with its mineralogical diversity, remains an important reservoir of water/hydrogen, and provide information on the potential evolution of the primitive Earth. Finally, mineral inclusions in diamonds have provided unique windows into the deep Earth, allowing us to gain further knowledge on the nature and extent of the deep-water cycle. This session invites contributions (experimental, numerical, petrological, field-based and analytical) describing water/hydrogen storage and mobility, and studies which shed new light on crustal, magmatic or mantle processes and Earth's volatiles budget at large, to better decipher our invisible ocean. *Keynote Speaker:* Nathalie Bolfan-Casanova (Laboratoire Magmas et Volcans, Université Clermont-Auvergne) *More details*: https://emc-2024.org/welcome/ We hope to see you there! Sylvie Demouchy Mike Jollands Davide Novella