The neurodevelopmental outcome of at-risk infants in the neonatal intensive care unit (NICU) is concerning despite steady improvement in the survival rate of these infants. Our current management is often complicated by delayed realization of cerebral deficits due to late manifestation and lack of effective screening tools and neuroimaging/monitoring techniques that are suitable for sick neonates at the bedside. Near infrared specstrocopy (NIRS) is a noninvasive, safe, and portable technique providing a wide range of cerebral hemodynamic contrasts for evaluating the brain. The current state of NIRS technology can be devided into three generations. The first generation represents conventional trend monitoring oximeters that are currently the most widely used in the clinical settings, while the second generation focuses on improving the quantitive accuracy of NIRS measurements by advanced optical techniques. The emergence of diffuse optical imaging (DOI) represents a third generation which opens up more potential clinical applications by providing regional comparisons of brain oximetry and functions either at rest or in response to interventions. Successful integration of NIRS/DOI into the clinical setting requires matching the different capabilities of each instrument to specific clinical goals.