The knowledge of the morphofunctional features from the coronary microcirculation is essential for understanding its role in cardiac physiological work and in the pathogenesis of coronary microvascular dysfunction (CMD). The cardiovascular system comprises the heart and blood vessels, including arteries, veins, and capillaries, both systemic and pulmonary. Arterioles are the primary site of vascular resistance and have only one to two layers of smooth muscular walls. Chapter One will provide an overview of the coronary microcirculation, its functions and regulatory mechanisms. The importance of CMD will be summarised in the context of diverse clinic scenarios, considering its pathogenesis, assessment and therapeutic management. The purpose of Chapter Two is to understand the role of arteriolar endothelial dysfunction in CVDs and its underlying mechanisms. Chapter Three will explore the physiopathology, epidemiology, and the diagnosis and treatment of hypertensive retinopathy. Chapter Four reports on angiogenesis, a critical process for reproduction in mammals, which consists of arterioles and blood vessels formation from the existing ones.