A ‘clair-obscur’ normativity. In French, Historians of art use it when they refer to an abrupt association of zones made out of very dark shadows together with dazzling lights, like da Caravaggio used to paint. It applies successfully to nanotechnologies, which points out to this set of technologies that are being developed at a billionth of a meter. At this scale, matter shows new and unexpected properties, which could potentially lead the way to numerous applications but how do we regulate it? Lacour's edited volume should be of interest to lawyers and regulators interested in this subject. It borrows this formula of the clair-obscur to characterize a fluctuating normative environment which surrounds nanotechnologies’ development.