Christophe Tournassat is a Professor at the University of Orléans, at the Institut des Sciences de la Terre d’Orléans (ISTO, France), and a Visiting Faculty in the Energy Geosciences Division, Earth and Environmental Sciences Area at Lawrence Berkeley Laboratory (LBNL, USA). Christophe Tournassat holds B.Sc. and M.Sc. degrees in Earth Sciences from the Ecole Normale Supérieure de Lyon, a Ph.D. in Environmental Geochemistry from the University of Grenoble, and an "Habilitation à diriger des recherches" in Geology from the University of Nantes, France. Christophe Tournassat has been working for more than twenty years on scientific issues related to radioactive waste storage, first as an Andra Ph.D. fellow, then as a scientist at BRGM and LBNL, and now at the University of Orléans and LBNL. His scientific interest covers a range of topics from thermodynamics and kinetics of low temperature water/solutes/rock interactions to multi-scale numerical modeling of retention and transfer processes in geological media. He co-develops, with Carl Steefel, the code CrunchClay, which can simulate biogeochemical reactions coupled with non-Fickian/non-Darcian transport processes occurring in nanoporous media such as clay rocks and cementitious materials. Christophe Tournassat is associate editor of Geochimica et Cosmochimica Acta, and is member of the editorial board of Applied Clay science.