In Chapter 9, we gave an exposition of the most generally useful and practical spectroscopic methods currently employed in modern organic laboratories. However, in our discussions of nmr spectra, we passed rather quickly over the basis of understanding why some lines are broad and others sharp, why rate effects can cause chemical shifts to be averaged, and how to correlate spin-spin splitting with the energies of nmr transitions. These topics will be discussed in this chapter along with a brief explanation of the remarkable effects on nmr spectra associated with some kinds of chemical reactions, namely, chemically induced dynamic nuclear polarization (CIDNP). In addition to the spectroscopic methods covered in Chapter 9, there are a number of other spectroscopic techniques that are less generally used, but can provide, and have provided, critical information with regard to specialized problems. Because some of these are relatively new and may become more widely used in the next few years, it is important that you be aware of them and their potentialities. However, because, they may be peripheral to your present course of study, we have reserved consideration of them to this chapter.