The 4th generation light source (X-ray Free Electron Laser) is a facility that accelerates electrons up to the light speed and creates a strong x-ray, allowing scientists to observe ultrafast phenomena in nano-worlds. It is a building-sized super-microscope, in a simple description, that can analyze biostructures and their dynamic reactions at the atomic level.

The 4th generation light source distinctly sets itself apart from those of previous generations in many ways. The most noticeable difference is its long, rectangular shape unlike the circular form of the 1st, 2nd, and 3rd generation models, which use the synchrotron radiation emitted to the tangential direction as the orbit of the electron beam is bent out when the electron beam passes through a dipole magnet. The XFEL, the 4th generation light source, produces a light much coherent like a laser that can travel a long distance without breaking its collimation and still stay strong.

The XFEL has an extremely short wavelength, a speed faster than lightening, and the brightness 10 billion times greater than the 3rd generation light source (10 quadrillion times of the sunlight). With this ultrafast, ultra-bright, and ultra-small light, it becomes possible for scientists to observe matter at nanoscale levels, as small as 1/40 of the thickness of human hair, and capture moments as short as one ten-trillionth of a second in which molecules are bonding and breaking.

Scientists anticipate that using the XFEL they can tap the uncharted frontier and pioneer groundbreaking innovations in science and technology. As the XFEL is extremely useful in the examination and analysis of protein structures and molecular chemical reactions that require utmost sensitivity, it may now be promising to find solutions for incurable diseases such as dementia and diabetes. The XFEL is expected to play a key role in making a giant leap not only in the medical, but also in new materials and semiconductor industries.