STATE OF THE ART The cardiovascular system (both macro- and microcirculation) undergoes extensive maturation throughout fetal, perinatal and pediatric life. Extreme preterm birth interferes with the normal development of the cardiovascular and microcirculatory systems. Disruption in vascular ontogenesis leads to abnormalities in the microvascular structure and circulation in various organs, such as retina (retinopathy of prematurity [O'Connor et al.]), kidney (abnormal glomerulogenesis [Sutherland et al.]) and glycocalyx in sublingual capillaries [Nieuwdorp et al.], among microvascular-driven disruptions observed in other organs (e.g. periventricular leukomalacia [Takashima et al.], bronchopulmonary dysplasia [Gien et al.]). Besides the well known retinopathy of prematurity, microvascular growth drives glomerulogenesis in the kidney and terminates after 34-36 weeks of gestational age under normal fetal conditions.