What will be the possible alternatives to semiconductor-based computing devices beyond Moore's Law? In HP labs, we have experimented molecular electronic devices with bistable electronic properties, which offer opportunities for future nanoscale high-density electronic circuits. In these devices, metal wires with the widths at sub-50 nm scale were fabricated by imprinting lithography as contact electrodes and connections. Langmuir-Blodgett molecular thin films with switchable electronic properties were assembled between the nanowire electrodes to form molecular electronic devices. Bistable electronic statuses with high on-off ratio and reversible switching properties have been observed in these devices. A crossbar network of the nanowire arrays can form circuits with memory functions at a density of ~40 Gbit/cm². The design and fabrication of the molecular devices, circuits, and their applications will be discussed.