The spectroscopist in the past has been a fortunate fellow. When he could no longer find something new to measure with his old spectrometer (or if he became bored with repeated use of the same old frequencies) he could always move on to a new place in the spectrum, provided of course that he could generate and detect radiation there. Until very recently there was a vast unexplored island in the electromagnetic spectrum, the region between the infrared waves and the conventional radio waves, now known as the microwave region