21^st century computing will be performed on machines constructed by assembling atoms or molecules with nanotechnology tools at the nanometer scale. The BioCube, developed at the Ecole Polytechnique Fédérale de Lausanne (EPFL), is a prototype that embodies the operating principles of such a machine, blown up a billion times and organized as a cube of 64 nodes. The complete BioCube foreshadows a nano-computer, opening the way to the realization of three-dimensional artificial organisms inspired by biology, capable of growth, of self-repair, and of self-replication.