The primary tool used to investigate single-molecule chemistry and physics is a scanning tunneling microscope (STM). STM was invented by Gerd Binnig and Heinrich Rohrer in 1981. They received the Nobel Prize in Physics in 1986 for its invention. Scanning tunneling microscopy raster scans a sharp conducting tip over a conductive surface. In constant current mode the number of electrons flowing between the tip and sample is kept constant by adjusting the height of the tip. This is a highly sensitive technique that allows for atomically-resolved topographical and electronic maps of the surface.