Over the past decades, self-assembly has attracted a lot of research attention and transformed the relations between chemistry, materials science and biology. The paper first describes three different strategies of self-assembly in nanotechnology. -1- Hybridization ( using the building blocks of living systems for making devices and machines) ; -2- Biomimetics (making artefacts mimicking nature); -3- Integration (a composite of the two previous strategies). The second section examines the distinction between self-assembly and self-organisation in the perspective of the long-term chemists' aspiration to make life. The third section addresses ethical issues raised by a technique of design “without human intervention”. After the delegation of a number of mechanical or logical operations to machines, the time has come to delegate the construction of machines itself to matter. What can be the impact of this “next step” on the responsibility of designers?