Nanomaterials are designed to have structural features below 100 nanometers. Their chemical and physical characteristics are interesting for many technical and medical applications. However, the exact interaction of nanomaterials with biological targets is still unclear. Especially nanoparticles (at least two dimensions _ 100 nm) raise many concerns: They pass cell membranes and epithelial and endothelial barriers, the effectiveness of existing health and safety measures is disputed and their environmental fate and impact is unknown. Several national and international projects to investigate such risks are running or about to start. However, there is insufficient cross-talk between these initiatives, and it is difficult for European researchers and stakeholders to access the knowledge these projects created. Recently, a multidisciplinary network of scientists from 20 European countries was launched. It aims at facilitating coordination and collaboration between researchers so that they can create knowledge that allows assessing the impact of nanomaterials. Such research needs to combine (eco)-toxicological approaches and health effect studies with information about human exposure and environmental fate of nanomaterials. The network promotes the development of new and the adaptation of existing methods. The knowledge created will be made available to scientists and stakeholders to support the definition and implementation of knowledge-based (rather than believe-based) safety, health and environment strategies for a safe and responsible development, production, use, and disposal of nanomaterials.