Electronic confinement at nanoscale dimensions remains a central means of science and technology.  I will describe a novel method for producing electronic nanostructures at the interface between two normally insulating oxides, LaAlO3 and SrTiO3.  These structures and devices are "written" by a conductive atomic force microscope probe in ambient conditions at room temperature, and can be erased and reconfigured.  The spatial dimensions of these structures are comparable to the width of a single-wall carbon nanotube (~2 nm).  A wide variety of devices can be created, including nanowires, tunnel junctions, diodes, field-effect transistors, single-electron transistors, superconducting nanowires, and nanoscale THz emitters and detectors.   This new, on-demand nanoelectronics platform has the potential for widespread scientific and technological exploitation.