Knowledge of physical and chemical properties of planetary regolith grains play an important role in several fields of Solar System research. For instance, the interaction of airless/icy bodies surfaces with the Solar Wind, or magnetospheric plasmas, is strongly constrained by such properties (as e.g. porosity). Planetary surfaces spectroscopy, especially reflectance measurements in the UV-Vis-IR ranges also depend strongly on regolith grain size distributions and surface porosity. On top of that, knowledge of regolith cohesion and charging state is becoming of importance to derive environmental specifications for planetary surface probes. The goal of this session is to sollicitate observational/experimental/modelling results in order to trigger idea exchanges on those aspects. Contributions are welcome on remote or in-situ regolith properties measurements technics and experiments, as well as laboratory investigations of natural grains and regolith simulant properties (including grains charging behaviour). Theoretical developments on the topic are also most welcome.