The crystal structure of clay particles determines a particular geometry such as lamellar (e.g., montmorillonite nanolayers or more robust kaolinite particles) and fibrous (e.g., sepiolite ribons or imogolite nanotubes) shape. Moreover unlike surface properties and reactive sites are located on the different parts of particles, e.g., on the faces or edges of lamellae, and the inner or outer sides of nanotubes. The geometry together with the different surface chemical character results in high active surface area and terrific surface charge heterogeneity under changing conditions, which governs the colloidal properties of dispersions. This session covers the characterization and modification of charge and active sites on clay surface in relation to the particle interactions (dispersion, aggregation) mainly in aqueous medium, the effect of pH and salt concentration on colloidal properties, in particular on the thixotropy, as well as the plastic and elastic properties of coagulated particle networks. Since the definite role of clay minerals in the environment and their applications are mostly based on their colloidal and surface chemical properties, talks and posters are welcome on the recent problems of environmental pollution, the dynamic and fate of charged organic pollutants, complexants, heavy metals and radionuclides, as well as the advancements in nanotechnology using lamellar or perhaps fibrous clay particles.