The assembly of ultrathin ZnSe nanowires over large areas (see figure) is achieved by a Langmuir-Blodgett technique in a single step with uniform registry, and without any further secondary technique for alignment. Ultrahigh packing density of junctions, exceeding over 60 x 10(3) mu m(-2) is achieved by subsequent deposition of a second two-dimensional nanowire assembly with a controlled angle between the two layers. The resulting network notably surpasses the limit of conventional fabrication techniques.