This book offers an extensive review of the most recent data on the pathophysiological role of structural and functional alterations in the microcirculation, particularly focusing on hypertension and diabetes. It covers several relevant and innovative aspects, including the possible mechanisms involved in the development of microvascular remodeling and rarefaction, the technical approaches available for the detection of microvascular alterations, including non-invasive evaluations, the prognostic role of changes in small resistance artery structure, the possibility of preventing or regressing such alterations with appropriate treatment, and the potential clinical advantages of such intervention. A number of innovative areas of research are considered, including the role of the immune system, inflammation and oxidative stress in the development of microvascular alterations. Lastly, it examines the availability of recent non-invasive methods for the evaluation of small resistance artery morphology in the retina, which in the near future may provide a useful tool for the stratification of cardiovascular risk and even for clinical decisions regarding drug treatment, thus providing physicians with a clinically relevant instrument for improving and optimizing the management of hypertensive and diabetic patients. The book provides valuable, clinically relevant information for specialists (cardiology, internal medicine, and endocrinology) and general practitioners, and also offers novel and stimulating data to basic and clinical researchers.