Our knowledge about the composition, structure and properties of the Earth's interior is severely constrained by its inaccessibility to direct observations. Therefore, interpretation of geophysical data in terms of mineralogical and petrological models of the mantle and core is entirely dependent upon experimental data collected at the relevant pressures and temperatures as well as numerical experiments. This session will focus on the recent advances on crystallographic methods which can be used simultaneously with other techniques for the study in situ of phase equilibria, element partitioning, melting, elasticity and phase transformations of minerals.