Size Matters Less X-ray crystallography is a central research tool for uncovering the structures of proteins and other macromolecules. However, its applicability typically requires growth of large crystals, in part because a sufficient number of molecules must be present in the lattice for the sample to withstand x-ray—induced damage. Boutet et al. (p. 362 , published online 31 May) now demonstrate that the intense x-ray pulses emitted by a free-electron laser source can yield data in few enough exposures to uncover the high-resolution structure of microcrystals.

High-Resolution Protein Structure Determination by Serial Femtosecond Crystallography