When the construction of a political space demands shared systems of measurement, ensuring that everything is made comparable, coding categories and procedures are brought into place. Attributing singular cases to measurable categories was for a long time a prerogative of the State, but new systems of metrology are now broadening the range of players. With this traversal, we aim to start deconstructing these metrological systems, both old and new, to prompt different readings of the rhetoric behind them. By focusing on the social and political dimensions, the aim is to understand how metrology operates, when knowledge means power.