As electronic circuits shrink from finely etched lines in silicon wafers to nearly elusive proportions, researchers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory and Columbia University are studying how electrons flow through a molecular junction—a nanometer scale circuit element that contacts gold atoms with a single molecule. Their findings reveal the electrical resistance through this junction can be turned 'on' and 'off' simply by pushing and pulling the junction—a feature that could be used as a switch in nanoscale electronic devices.