Nanotechnology is set to change the world. Nanotechnology is increasingly talked about with the same breathless excitement that surrounded biotechnology and information technology at the start of the 1990s. Nanotechnology has caught the attention of several nongovernmental organizations (NGOs) that have spent the past decade campaigning against genetically modified (GM) crops and foods. A debate about its risks, is rapidly taking on a sharper focus around issues of nanoparticle toxicity and the need for tighter regulation. This work explores three dimensions of uncertainty in emerging debates over nanotechnology.