Cloudscape

Suppose that a wall of nanorobots would form in a body part (eg an arm) along the tissues; wherever they are, they imitate the function of the cells next to them; if there are no cells next to them, as in a cavity or vein, there aught not to be any nanorobots at all. In this way, every organic structure retains its normal function, even tendons, veins, and nerves. This wall then thickens, so that it becomes part of the body part, indirectly keeping the two halves together so that it still functions normally. This wall of nanorobots could then keep growing indefinitely, so that the body part would become extendable. In this way, one could, in principle, temporarily extend one's arm for meters. Admittedly, doing this safely would require advanced technology which today can only be carried out in science-fiction.