This paper argues that the typical analysis of the questions of risks posed by emerging nanotechnologies (in particular by nanoparticles) provided by much of the current debate is in a general and consequentialist framework, which appears reductive and problematic. On the one hand, this is due to the typical epistemological features of these technologies and, on the other hand, to the metaphysical research program that serves as their background. The centrality of risks exercises a sort of control of the debate by imposing the relevant questions and excluding other important topics. Furthermore, informed by the promise of great transformative potential and by the identification of knowing with making, nanotechnologies organize their program around a rich and multi-faceted idea of control of matter and this conceptualization is important also for the understanding of risks. In this paper it will be argued that much of the current ethical discourse around these technologies, which takes the question of risk as the central question, reduces ethics to a narrow form of risk assessment and, thus, a different approach is required. Alternative approaches that emerge in the present literature will then be discussed, i.e. ethics as a more sophisticated form of prudence. Finally, the analysis of the metaphysical ideas surrounding nanotechnologies will be highlighted as a fruitful way for deepening the understanding of the ethical relevance of nanotechnologies for a renewed understanding of risks, capable of taking into account their socially constructed and situated character. For a proper analysis of the ethical and social challenges emerging from nanotechnologies, an inquiry into their socio-economic context also appears to be fundamental since technologies are not ethically neutral but are rather constructed in a social and historically situated environment.