1. Nanotechnologies: challenges and risks

The twentieth century has witnessed spectacular advances in our understanding of matter, whether inert or living. Following a long series of discoveries, whether in terms of elaboration methods such as chemical synthesis techniques, epitaxy or lithography, or observation methods such as the electron microscope, and more recently the scanning tunneling microscope or the atomic force microscope, it is now possible to "see" and act on the scale of the molecule or even the atom. These technical and scientific developments have given rise to nanoscience, the study and manipulation of matter on the nanometer scale (10 ^–9 m or one billionth of a meter). This is not a discipline, but rather the convergence of physics, chemistry, biology and engineering around this length scale.