Inside a vacuum chamber cooled at very low temperatures, they move a scanning tunneling microscopy probe over the surface of a silicon wafer, and with it, in the locations that they choose, they can build some carbon atom structures attached to the silicon surface, atom by atom, in a reproducible way.

This kind of control of atomic structures, where the position of every individual atom can be controlled, is very impressive, but for now this is pure research. Any practical applications are more than a decade in the future.

Techniques derived from this might be used some day either for making some kind of integrated circuits or for making some kind of masks for the production of such circuits, but there is no way to use this directly for the production of some material needed in great quantities, like nanotubes for a space elevator.

For a material needed in great quantities, if you build it atom by atom, there must be billions of such building processes done concurrently, like in a living being, in order to achieve an acceptable growth rate. For now, they use a microscopy probe to attach the atoms one by one and you could not make a sufficient number of these that work concurrently.