The Joint Research Center (JRC) published on October 19, 2015, a report entitled Towards a review of the EC Recommendation for a definition of the term “nanomaterial”: Part 3: Scientific-technical evaluation of options to clarify the definition and to facilitate its implementation. The report provides JRC’s scientific-technical evaluation of options to clarify the European Commission’s (EC) 2011 Recommendation on a definition of nanomaterial. In 2013, JRC started to develop a series of three scientific-technical reports based on a list of tasks addressing specific points of the EC’s Recommendation. In this third report, JRC describes scientific and technical options intended to clarify the wording and facilitate the implementation of the definition. JRC states that the scope of the definition regarding the origin of nanomaterials should remain unchanged, addressing natural, incidental, and manufactured nanomaterials. According to JRC, because of the regulatory purpose of the definition, there is little evidence to support deviating from size as the sole defining property of a nanoparticle or from the range of 1 nanometer (nm) to 100 nm as the definition of the nanoscale. JRC notes that clarification of some terms used in the definition and additional implementation guidance would be useful. JRC cautions, however, that relying only on guidance documents for essential parts of the definition could lead to unintended differences in the implementation and decision making.