On Mar. 28, 2011, the Priestley Medal was awarded to Ahmed H. Zewail by the American Chemical Society “to recognize distinguished services to chemistry.”

The award recognized Zewail’s “ultraslow-motion” imaging techniques for the study of ultrafast processes in chemistry, biology and materials science, through the use of femtochemistry. This allows the study of chemical processes on the femtosecond timescale by using lasers to capture frames of the motion of atoms and molecules as they undergo reactions.

Zewail also developed four-dimensional electron microscopy and associated methods to visualize materials and biological cells with unprecedented resolutions in both space and time.