The role of the microcirculation is increasingly being recognized in the pathophysiology of cardiovascular disease.1,2 The microcirculation is a major site of damage in most target organs of cardiovascular disease, such as the heart, brain, and kidney. Both functional and structural alterations in the small arteries, arterioles, and capillaries are the basis of target organ damage. Furthermore, the microcirculation is the major site of control of vascular resistance. This makes it a central player in the etiopathogenesis of diseases characterized by an increased vascular resistance, such as hypertension. Detailed mechanistic studies in both humans and animal models of cardiovascular disease have revealed the nature of microcirculatory dysfunction. Large-scale epidemiological studies in the last 2 decades have identified the associations among deranged microvascular perfusion, structure, target organ damage, and subsequent cardiovascular disease.3 Major technological developments now allow study of the microcirculation both in mechanistic and epidemiological studies. The purpose of this Brief Review is to provide a critical appraisal of these developments and their particular impact on hypertension research. ### Assessment of the Microcirculation The Table gives an overview of the major methods to assess the microcirculation. Intravital microscopy has been used by many groups in experimental models to study microcirculatory (dys)function. It has been the primary technology underlying our present knowledge of microcirculatory function in health and disease. Intravital microscopy is the optical imaging of living organisms. The tissue to be studied is prepared by surgical techniques and microscopes, usually in combination with high quality video recorders, is used to visualize the microcirculation. Originally this technique was used in relatively transparent tissues like the bat wing, hamster cheek pouch, or rat mesentery. Later developments using trans- and epi-illumination have allowed wider access to the microcirculation of other tissues, such as skeletal muscle, the brain, and the heart. The recent introduction of …