It is intensive, of high brilliance and its spectrum can be calculated exactly: the synchrotron radiation of the “Metrology Light Source” (MLS) of the PTB. These and a number of further characteristics make it exceptionally interesting for broad application in science and technology. On 23 June, the PTB put its own low-energy storage ring for the production of synchrotron radiation, the MLS, in Berlin-Adlershof, into operation. It is optimized for the spectral range between the extreme ultraviolet (EUV) and terahertz radiation which is continuously available at only a few sites worldwide. This spectrum is suited, for example, to applied research in the field of EUV lithography for the production of computer chips of the next generations and in the field of terahertz technology which will in future play an important role in safety engineering and materials testing.