Electrical Energy Measuring Techniques, Quantum Electronics, Semiconductor Physics and Magnetism, Quantum Electrical Metrology Division 3: Chemical Physics and Explosion Protection (site: Braunschweig) with the following departments: Metrology in Chemistry, Analytics and Thermodynamic State Behavior of Gases, Thermophysical Quantities, Physical Chemistry, Explosion Protection in Energy Technology, Explosion Protection in Sensor Technology and Instrumentation, Fundamentals of Explosion Protection Division 4: Optics (site: Braunschweig) with the following departments: Photometry and Applied Radiometry, Imaging and Wave Optics, Quantum Optics and Unit of Length, Time and Frequency Division 5: Precision EngineerinꞋ (site: Braunschweig) with the following departments: Surface Metrology, Dimensional Nanometrology, Coordinate Metrology, Interferometry on Material Measures, Scientific Instrumentation Department Division 6: Ionizing Radiation (site: Braunschweig) with the following departments: Radioactivity, Dosimetry for Radiation Therapy and Diagnostic Radiology, Radiation Protection Dosimetry, Ion and Neutron Radiation, Fundamentals of Dosimetry, Operational Radiation Protection Division 7: Temperature and Synchrotron Radiation (site: Berlin-Charlottenburg and Adlershof) with the following departments: Radiometry with Synchrotron Radiation, Cryophysics and Spectrometry, Detector Radiometry and Radiation Thermometry, Temperature, Heat and Vacuum Division 8: Medical Physics and Metrological Information Technology (site: Berlin-Charlottenburg) with the following departments: Medical Metrology, Biosignals, Biomedical Optics, Mathematical Modeling and Data Analysis, Metrological Information Technology The Presidential Staff Office and the Press and Information Office as well as the Divisions Z (Administrative Services) and Q (Scientific-technical Cross-sectional Tasks) report directly to the Presidential Board. Division Q comprises, among other things, the Academic Library, the Legal Metrology and Technology Transfer Departments, the Technical Services, and the Technical Cooperation Department. History Two essential factors which led to the founding of the Physikalisch-Technische Reichsanstalt (Imperial Physical Technical Institute – PTR) were the determination of internationally valid, uniform measures in the Meter Convention of 1875 and the dynamic industrial development in Germany in the 19th century. Already in the Franco-German War (1870/71), the stagnation in scientific mechanics and in the science of instruments had become evident in Germany. Increasingly precise metrology was required for industrial production. A considerable impact on the initiative for the founding of a state institute for metrology in order to promote the national interests of the economy, of trade and of the military was made – in particular – by the upcoming electrical industry under the direction of the inventor and industrialist Werner von Siemens. In contrast to the units of length and weight, no recognized methods and standards existed at that time in the field of electrical metrology. The lack of