Nanomaterials are used every day for countless applications, yet their implications for health and the environment are not fully understood. In fact, the majority of commercialised nanomaterials remain under the radar of regulators. At the OECD level, member states work to develop a set of Test Guidelines and Guidance Documents to clarify how manufactured nanomaterials (MN) need to be tested to provide information and check their safety. Read our new briefing to learn about the state of play, and what still needs to happen to make nanomaterials safe for all!