The international project with twelve participating countries; nine shareholders at the time of commissioning (Denmark, France, Germany, Hungary, Poland, Russia, Slovakia, Sweden and Switzerland), later joined by three other partners (Italy, Spain and the United Kingdom), is located in the German federal states of Hamburg and Schleswig-Holstein.

A free-electron laser generates high-intensity electromagnetic radiation by accelerating electrons to relativistic speeds and directing them through special magnetic structures.

[2][3] [4][5][6][7] The 3.4-kilometre (2.1 mi) long tunnel for the European XFEL housing the superconducting linear accelerator and photon beamlines runs 6 to 38 m (20 to 125 ft) underground from the site of the DESY research center in Hamburg to the town of Schenefeld in Schleswig-Holstein, where the experimental stations, laboratories and administrative buildings are located.

[8] The use of superconducting acceleration elements developed at DESY allows up to 27,000 repetitions per second, significantly more than other X-ray lasers in the U.S. and Japan can achieve.

The instrument Single Particles, Clusters, and Biomolecules & Serial Femtosecond Crystallography (SPB/SFX)[13] can provide data on objects in the micrometre range up to atomic resolution.

The ultrashort FEL pulses of less than 50 fs duration in combination with a synchronized optical laser allow for capturing ultrafast nuclear dynamics with very high resolution.

[18] The scope of the MID instrument are material science experiments using the unprecedented coherent properties of the X-ray laser beams of the European XFEL.

The scientific applications reach from condensed matter physics, studying for example glass formation and magnetism, to soft and biological material, such as colloids, cells and viruses.

The extremely brilliant and highly coherent X-ray beams will open up unseen possibilities to study dynamics in disordered systems down to atomic length scales, with timescales ranging from femtoseconds to seconds using techniques such as XPCS.

[20] The experimental beamlines enable unique scientific experiments using the high intensity, coherence and time structure of the new source to be conducted in a variety of disciplines spanning physics, chemistry, materials science, biology and nanotechnology.

[21] The German Federal Ministry of Education and Research granted permission to build the facility on 5 June 2007 at a cost of €850 million, under the provision that it should be financed as a European project.