Diabetes mellitus is increasing in incidence, prevalence, and importance as a chronic disease throughout the world. The International Diabetes Federation projects that by 2030 there will be 438 million people with diabetes on a global scale. In the United States, the Centers for Disease Control calculates that 25.8 million people (or 8.3% of the population) have diabetes and nearly 2 million Americans develop diabetes each year. Thus, the burden of diabetes is enormous in terms of the magnitude of the population affected.  There has been an exciting explosion of knowledge about fundamental mechanisms related to diabetes. We have gained insights into the pathogenesis both of type 1 and type 2 diabetes, and with that, the prospect of implementing prevention strategies to delay or interdict the disease processes. Great progress has been made in islet transplantation, which offers the potential of reversing diabetes, while approaches to islet replacement by regeneration or stem cell therapy are in their infancy. Whether diabetes prevention will come from advances in understanding the processes of islet neogenesis and proliferation, from genetic engineering, or from protecting xenoislets or stem cells from immunologic attack remains unclear. All are potential avenues of pursuit. This newly revised, comprehensive, four-color Atlas of Diabetes, 4^th Edition, is extensively updated with references to the current literature.  Developed by leading authorities in the field, this Atlas offers an indispensable collection of images, including algorithms, tables, charts, and schematic drawings.  It continues its role as a leading reference work and an invaluable contribution to the field.