The microcirculation plays a major role in oxygen delivery and organ perfusion, and is largely involved in the pathophysiological alterations of shock states. It has been a focus of research for a long time, but human clinical and physiological studies have been limited by a lack of reliable techniques available at the bedside. Intravital microscopy, although of interest in experimental studies, is not feasible in human studies. Laser Doppler techniques can measure blood flow, but do not take into account the heterogeneity of the microcirculation. Recently, the Orthogonal Polarized Spectral (OPS) imaging technique has enabled the study of the microcirculation in humans. This technique has allowed a better definition of microcirculatory alterations in disease states, defined the role of some medical interventions, and been used to predict outcome. In this text, we briefly describe the techniques available to study the microcirculation and review experimental and human studies in this domain.