The Royal Society and Royal Academy of Engineering's report on nanotechnologies - Nanoscience and nanotechnologies: opportunities and uncertainties - was published on 29 July 2004. The report illustrates the fact that nanotechnologies offer many benefits both now and in the future but that public debate is needed about their development. It also highlights the immediate need for research to address uncertainties about the health and environmental effects of nanoparticles - one small area of nanotechnologies. It also makes recommendations about regulation to control exposure to nanoparticles. The report will be of interest to a wide range of international stakeholders including policy-makers within and outside Government, researchers working in academia and industry and civil society groups.