When modern chemistry emerged, carbon was viewed as an abstract, albeit material substrate underlying a range of phenomenologically simple and compound bodies. In this respect, carbon may be presented as an exemplar, a didactic tool illustrating the abstract mode of existence of chemical elements, as opposed to the concrete, empirical existence of simple substances. At least it was the way carbon wrote itself in chemistry textbooks and in metachemical attempts at defining the status of the element as that what persists through chemical transformations. But carbon continued to maintain and to compose other modes of existence, among which: carbon as the backbone of life and pillar of chemical industry (and of academic organic chemistry), and carbon as material. I will focus more specifically on the singular trajectory leading from carbon fibers to carbon nanotubes—a technoscientific renaissance in which carbon, pushed at the edge of the material, comes back into being as a menagerie of bizarre allotropes (nanotubes, fullerenes, graphene, and many more) all made up of pure surfaces, rolled, bent, folded or unfolded. As in Kandinsky’s system of basic figures making the world of painting (Point, Line, Plane), each one can be generated out of another: graphene can be rolled into tubes, fullerenes are capping the tubes, tubes can be opened to make graphene ribbons, and so forth. Carbon nanomaterials are no more defined by their elementary properties (“what is it?”), nor by their dispositions (“what are they capable of?), but rather by their affordances: “what might they afford?” or “what might be performed with it?”—surfaces of affordance which generate a cornucopia of promises about high-tech applications as well as new research fields such as giant molecules or experimental 2-D physics. Finally, by considering the multiplicity of modes of existence of carbon, I will come back to the ontological question “what”, or rather “who is carbon?”