This paper aims to review different discourses within the emerging field of ethical reflection on nanotechnology. I will start by analysing the early stages of this debate, showing how it has been focused on searching for legitimacy for this sphere of moral inquiry. I will then characterise an ethical approach, common to many authors, which frames ethical issues in terms of risks and benefits. This approach identifies normative issues where there are conflicts of interest or where challenges to the fundamental values of our society arise. In response to the limitations of this approach, other commentators have called for more profound analysis of the limits of our knowledge, and have appealed to values, such as sustainability or responsibility, which should, they suggest, inform nanotechnological development (I will define this approach as a "sophisticated form of prudence"). After showing the ways in which these frameworks are limited, I will examine more recent developments in debates on nanoethics which call for the contextualisation of ethical discourse in its ontological, epistemic and socio-economic and political reflections. Such contextualisation thus involves inquiry into the 'metaphysical research program' (MRP) of nanotechnology/ies and analysis of the socio-economic, political and historical reality of nano. These ideas offer genuinely new insights into the kind of approach required for nanoethical reflection: they recover a sense of the present alongside the need to engage with the past, while avoiding speculation on the future.