FLASH at DESY was the world’s only and first free-electron laser (FEL) to generate radiation in the vacuum ultraviolet and soft X-ray regions when it started user operation in 2005. It enables researchers to explore the temporal evolution of physical, chemical, and biochemical processes happening on the femtosecond (fs) and picosecond (ps) timescales. Today, FLASH produces ultra-short laser light in the wavelength range from 4.2 to 45 nm. The pulse duration can be varied from <50 fs to 200 fs. FLASH is able to deliver several thousands of X-ray pulses per second with single pulse energies of up to 500 µJ. FLASH operation is financed 90% by the German and 10% by the regional governments of Hamburg and Brandenburg. Access to FLASH for European users has been supported by EC via IA-SFS/FP6, ELISA and CALIPSO/FP7. FLASH is one national facility of EuroFEL, a distributed RI of the ESFRI roadmap.