"Back at Caltech, my research was going strong, and we had four different laboratories busy with experiments and people. In one of these laboratories, we were continuing with our work on coherence; in others, advancing techniques for shorter time resolution and for developing an optical analog for nuclear magnetic resonance (NMR). In NMR, the spin of nuclei with their transitions at radio frequencies is used for a variety of applications, ranging from the studies of molecular structure to magnetic resonance imaging (MRI), which is now commonly used in hospitals throughout the world."