Electron-electron and electron-ion forces drive all processes in chemistry, yet for many years these interactions were difficult to capture in experiments because of the ultra-short time scales and distances involved.
Two advances in laser technology led to methods that overcome these problems. The first was the development 30 years ago of powerful ultrafast lasers with focused optical fields comparable to the binding fields in chemical bonds, exceeding one volt per Angstrom. These lasers led to new ways to control the interactions of electrons in atoms on their natural time scales.
The second advance was the development in the last decade of ultrafast x-ray lasers with Angstrom-wavelengths and even higher focused fields. These can be used to produce movies of molecules as they undergo bond rearrangements in tens to hundreds of femtoseconds (millionth-billionths of a second). Recent improvements in the x-ray source will soon enable measurements that can resolve attosecond-scale (billionth-billionth of a second) electron motion in x-ray-atom interactions.