Embodiments of the present invention are directed to methods for fabricating microscale-to-nanoscale interfaces. In numerous embodiments of the present invention, hybrid microscale/nanoscale crossbar multiplexers/demultiplexers provide for selection and control of individual nanowires through a set of microscale signal lines. In order to overcome the difficulty of aligning nanowires with submicroscale and microscale signal lines, at least a portion of the interconnections between nanowires and sub-microscale or microscale signal lines are randomly generated by one of various connection-fabrication methods. Addresses for individual nanowires, or groups of nanowires, can be discovered by testing the microscale-to-nanoscale interfaces.