On September 12-13, 2018, the Organization for Economic Cooperation and Development (OECD), NanoReg2, and GRACIOUS hosted a “Scientific Workshop:  Grouping of Nanomaterials.”  The Workshop brought together 120 nanotechnology specialists from Europe, North America, and Asia to discuss a bottleneck in nanomaterials development and testing.  The agenda and the following slides from the workshop have been posted online: