Image: Lee Park/Purdue University
Until 1981, the atom was a sort of imaginary entity. We knew it was there, of course, and we could even measure and observe it via a number of different techniques—including field ion microscopy—but we couldn't just go and look at an atom in the same way that we could peer into a microscope and look at some biological cells.Then, in 1981, Gerd Binnig and Heinrich Rohrer came along with the scanning tunneling microscope, which allowed scientists to look at surfaces at atomic scales for the first time. The pair won the Nobel Prize for the accomplishment in 1986. Here, in the latest of Physics World's 100 Second Science series, the physicist Peter Wahl explains how the thing actually works.