All engineering, although obviously science-based, contains a vital element: the art of engineering. In this lecture I hope to trace the development of microwaves during the past four decades or so, and to illustrate in this context the essential contribution that this second element has made. During this period, microwave techniques have been developed for many new applications, ranging from satellite systems and atomic clocks to intruder alarms and microwave ovens. The usable frequency range has been greatly extended, as has the instantaneous bandwidth available, typified by the invention of `frequency independent' antennae and wide-band waveguides such as microstrip. Coupled with all of this has been the parallel development of microwave measurements, not only in the accuracy obtainable and in the rage of frequencies covered by a single instrument, but also by the possibility of automatic measurement with microcomputer control. The practical achievements are remarkable, but I hope above all to bring out the elegance of the theoretical concepts on which they are based.