Metrology and fundamental constants : Varenna on Lake Como, Villa Monastero, 18-28 July 2006

This volume can be justified by the following three facts, the need to provide, from time to time, a coordinated set of lectures which present the relevant progress in Metrology, the increasing intertwining between Fundamental Physics and the practice of Metrological Measurements, and, third, the flurry of new and unexpected discoveries in this field, with a correlated series of Nobel Prizes bestowed to individuals working in Fundamental Constants research and novel experimental methods.One of the most fascinating and exciting characteristics of metrology is its intimate relationship between fundamental physics and the leading edge of technology which is needed to perform advanced and challenging experiments and measurements, as well as the determination of the values and interrelations between the Fundamental Constants. In some cases, such as the caesium fountains clocks or the optical frequency standards, the definition of the value of a quantity is, in the laboratory, in the region of 10-16 and experiments are under way to reach 10-18. Many of these results and the avenues leading to further advances are discussed in this volume, along a major step in metrology, expected in the near future, which could change the 'old' definition of the kilogram, still based on a mechanical artifact, toward a new definition resting on a fixed value of a fundamental constant.