Free electron lasers (FELs), which are driven by kilometer-long linear accelerators, emit bursts of short-wavelength light lasting one quadrillionth of a second. As a result, they can act as strobe lights for viewing the fastest events in nature — atomic or molecular motion — and therefore promise to revolutionize our understanding of almost any kind of matter. New research shows how to measure the super-short bursts of high-frequency light emitted from FELs. One of the co-authors of this study is Rick Trebino, professor in the School of Physics.