It is estimated that 86 million adult Americans have prediabetes and with that, a risk of developing T2DM (type 2 diabetes) within one in ten patients. About 29 million people have actual diabetes, most with T2DM. It was estimated in 2012 that about 208,000 people under the age of 20 have diabetes in the United States, but there is little data available on the prevalence of diabetes in the adolescent population. A recent study looking at 12-19 year olds from 2005-2014 found the prevalence of diabetes at 0.8%, with 28.5% undiagnosed and the prevalence of prediabetes 17.7%, more common among boys (22%) than girls (13.2%). With about 9% of the total US population having diabetes, this a public health issue of considerable proportions. In this book, the reader embarks on a journey through the medical history of the discovery and treatment of diabetes mellitus. It is the story of the human mind steadfastly seeking to understand its world — a story worth telling again and again — that has saved millions of lives from a premature death of misery in the 20th and now 21st century.