Compared to standard materials, nanomaterials dispose of specific properties, which make them attractive for manufacturing diverse products. At the same time, these properties result in a specific behaviour of nanomaterials in the environment. The environmental geoscientists from Vienna are investigating this environmental behaviour. With their research on the dispersion stability and agglomeration behaviour of nanomaterials, the Vienna working group has developed the OECD's first nanospecific test guideline (TG318). In doing so, the researchers filled an important knowledge and regulatory gap: Previous OECD guidelines for evaluating the ecotoxicity of so called ‘difficult to test substances’ had insufficiently addressed the specificity of nanomaterials. “With our work, we have been able to translate complex basic research into specific regulatory practice: The test guidelines we have developed have been internationally validated and therefore are valid in all OECD countries,” explains Frank von der Kammer. The guideline for the ecotoxicological testing of nanomaterials (GD317), which was lead developed by colleagues from the U.S. and Canada, and the guideline (GD318), that has substantially been developed by the Vienna research group, were both released in summer 2020. Two more guidelines are under development at the Department of Environmental Geosciences (https://edge.univie.ac.at/). The research received funding from the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety.