Emerging opportunities in structural biology with X-ray free-electron lasers

► X-ray free electron lasers produce X-ray pulses with extremely brilliant peak intensity and ultrashort pulse duration. ► The concept of 'diffraction-before-destruction' has been verified on biological samples at the Linac Coherent Light Source. ► The continuous diffraction patterns from single biological particles allow solving the classical 'phase problem'. ► Serial femtosecond crystallography has been used to determine the 3D structure of micron-sized protein crystals at high resolution. ► Coherent X-ray diffraction imaging of single virus particles has been experimentally demonstrated.