Some comments on fundamental constants and units of measurement related to precise measurements with trapped charged particles

Precise measurements of various physical quantities are being made with a much improved precision in experiments with trapped charged particles, many of which are reported in this Nobel symposium. In the present paper, these and other precise measurements are placed in the wider context of the successively more accurate determination of the fundamental physical constants which has taken place during the last decades. The role of systems of units of measurement, based on physical constants and the most accurate measurements, is recalled in providing a coherent framework in which the results of experiments made on different occasions and in different fields of physics may be related to one another