The world’s most powerful x-ray laser, the Linac Coherent Light Source II (LCLS-II) at SLAC National Accelerator Laboratory, officially produced its first x rays on 12 September. A $1.1 billion upgrade more than a decade in the making, the x-ray free-electron laser (XFEL) is now capable of firing 1 million x-ray pulses per second—8000 times as many as the first-generation LCLS, which began operation in 2009. Each pulse is 10 000 times as bright as those of the original LCLS. The new machine reestablishes the US facility as the top performer among the world’s five XFELs, surpassing the six-year-old European XFEL in Schenefeld, Germany.