On March 1, 2010, the European Commission (EC) issued a request, via the accelerated procedure, for a scientific opinion on the scientific basis for the definition of the term “nanomaterial” from the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR). According to the EC, its services “urgently need to elaborate a working definition of the term ‘nanomaterials’ to ensure the consistency of forthcoming regulatory developments to guide, as appropriate, the effective implementation of existing regulation, and to contribute to international work and dialogue on nanotechnology definitions.” The EC states that it needs “clarification on the size ranges and other relevant characteristics and corresponding metrics reported in the scientific literature, the types of physical and chemical properties particular to nanomaterials, the relevant thresholds, as well as the most appropriate metrics to express such thresholds.” The deadline is May 2010.