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Cover: This scanning electron micrograph shows crossbars of platinum nanowires. The wires at the center are about 10 nm in diameter and 30 nm apart. Molecular switches sandwiched at the intersections in that central region would create a random-access memory with a density of 32 gigabytes per square inch; the technique can be extended to obtain ultrahigh densities approaching 500 GB/in2. For more about the state of the art in molecular electronics circuitry, see the article by James Heath and Mark Ratner starting on page 43. (Image courtesy of Ferenc Krausz.)
