The metabolic syndrome (MetS) is a cluster of interrelated common clinical disorders, including obesity, insulin resistance, glucose intolerance, hypertension, and dyslipidemia (hypertriglyceridemia and low HDL-cholesterol levels). According to recently defined criteria, MetS is prevalent and is associated with a greater risk of atherosclerotic cardiovascular disease than any of its individual componentsáMany questions relating to its special pathophysiology still need to be clarified. With the purpose of compiling the state of the art on MetS, in 2006 we published the book entitled The Metabolic Syndrome at the beginning of the XXIst Century. A genetic and molecular approach (ed. Elsevier)áType 2 diabetes mellitus (T2D) is the first book of a collection of four (Obesity; Arterial hypertension; Atherogenic dyslipidemia) intended to update knowledge on the main medical disorders combining in MetS.áOne of the aims of this book is to illustrate the intellectual process and offer an ample and updated overview of the different viewpoints through which T2D is being considered. A second aim is to provide the reader with first-hand cutting-edge information on several (from molecular pathophysiology to genetic epidemiology) aspects of T2D and its relations with the so called ´classic´ components of the MetS, such as obesity, dyslipidemia, hypertension, and of course, their relationships with cardiovascular disease, but also on the newer components of MetS, such as inflammation molecules, prothrombotic state, or endothelial dysfunction, to mention just a few of them. Moreover, specific molecular and cellular issues have been focused in the context of glucose homeostasis, insulin action and insulin resistance mechanisms.