At PTB in Berlin and Braunschweig, time comes from atomic clocks, lengths are measured far into the nano-world, scientists do research on fundamental questions concerning the physical units, and the employees in the laboratories calibrate measuring instruments, meeting the most demanding requirements. Therefore, the Physikalisch-Technische Bundesanstalt (PTB) is among the top names in metrology worldwide. As Germany’s national metrology institute, PTB is Germany’s highest authority when it comes to correct and reliable measurements. It is the supreme technical authority of the Federal Ministry for Economic Affairs and Energy (BMWi) and employs a total of approx. 1900 staff members at its two sites (Braunschweig and Berlin).