X-ray free-electron laser (XFEL) source produces X-ray pulses more than a billion times brighter than the most powerful synchrotron source. The extremely intense X-ray pulses emerging from XFEL source, along with the appearance of serial femtosecond X-ray crystallography (SFX) technique enabled us to reveal radiation damage-free protein structures from nano-/micro-crystals. Current state of protein structure analyses using XFEL is described.
