Nanosciences and nanotechnologies are characterized by the fact that they are at the confluence of many scientific and, subsequently, technological fields. Thus, there are also numerous legal fields which apply to them, from health or privacy protection to labour or patent law. One of the objectives of the Law, in a broad sense, is to reconcile sometime opposing interests and liberties. Thus, to study the law in the field of nanotechnologies, one can try to follow these technologies through their life cycle, from their creation to their disuse and recycling. This methodology has been recommended by many different scientific and ethical agencies in Europe. I am going to target, in particular, three key steps in this life cycle. The first one is the “valorization” of nanosciences. How does patent law deal with the new reality that is nanotechnology? When do these entities leave the field of discovery, blue sky science, to enter the application field and to be patentable? What are nanotechnology's impacts on the philosophy that drives French and European patent laws, which finds its origins in the history of mechanics? The second step in the nano life-cycle is the European regulation of chemicals as it exists, confronted to the “nano” specificities. Are nanoparticles chemical substances? Is the existing legal framework adapted to their scale and shapes? At the other end of the R&D and commercialisation spectrum, nanotechnologies have enabled, for years now, the development of very small electronic devices which may present new risks to the protection that our law gives to privacy. What can we do to keep the progress nanodevices are promising and let their risks away ? More theoretically, finally, it is interesting to study how the growth of a new scientific field, such as nanoscience and nanotechnology, fields which are mainly defined by a reference to scale, can have an influence upon the legal system as a whole and the categories and premises upon which it is built.