As a result of the key advances made more than 30 years ago, specifically the ability to isolate islets of Langerhans from the pancreas, the ability to measure insulin accurately by immunoasay, and the development of microchemical techniques for studying cells and their components, many research volumes, symposium reports, and original papers have been produced. This explosion of interest has probably had at least three stimuli: 1. the inherent scientific interest in understanding secretion of the pancreatic ss-cell 2. the ss-cells relevance to a very common disease 3. the availability of funding from specific sources related to diabetes research, for instance, Juvenile Diabetes Foundation International and the British Diabetic Association. As a result of all this activity, detailed scientific literature including research reviews are readily available. Surprisingly enough, there are relatively few attempts to summarize this great bulk of knowledge in a way that is accessible to the newcomer to this field and this book is intended to bridge this gap.