After four centuries a quote from Galileo Galilei is still the most effective way to introduce a Metrology book: “Measure what is measurable, and make measurable what is not so”. Every human activity needs an objective measurement and every global process should be supported by a common standard. There are several handbooks, tutorials and journals that focus on the basic concepts of metrology, the uncertainty theory and the international reference standards. Moreover, the engineering literature is awash with measurement methods for each specific field. The aim of this book is different: it offers the most recent developments in some key sectors, its goal is to represent the state.