In Paris, October 1, 2013, groups from the “Chimie-Physique Matière et Rayonnement” Laboratory (UPMC-CNRS), together with SOLEIL Synchrotron, the University of Trieste (Italy) and Uppsala University (Sweden), showed that it is possible to obtain very accurately crucial information on the structure of molecules - such as the distance between the atoms that compose them, by repeating a famous optical experiment dating from 1801, this time on a microscopic scale. X-rays, electrons and atoms replace bulbs, visible light and slits. These results were recently published in PNAS.