Ahmed Zewail

For showing that it is possible to see how atoms move during a chemical reaction using femtosecond spectroscopy. Zewail's pump–probe technique fires an initiating laser pulse then probes the system after a delay of a few femtoseconds ($1\ \mathrm{fs} = 10^{-15}\ \mathrm{s}$), filming bond breaking and formation in real time and laying the foundations of femtochemistry.