Iron deficiency (ID) is the most common single nutrient disorder in the world. Pregnant women and children before pre-school age are at highest risk. Data from animal models provide evidence that early ID affected developing brain in specific regions and functions by varies processes include myelination, dopamine neurotransmitter system, and neurometabolism. These impacts appeared differential at different time of brain development and different brain regions, depending on the timing of ID. The reversibility of these effects also appeared to depend on the timing of ID. This project uses innovative neuropsychologic/ neurophysiologic and behavioral techniques, such as event-related potentials(ERP), ABR and VEP, to study brain functions and behavior related to ID including sensory ,motor, cognitive and social /emotional functioning, and address unanswered questions about brain and behavior impacts of different timing of ID(pre- and /or postnatal ID) in the human infants. This research has the potential to understand reversibility of effects depending on timing of ID and treatment as well as basic understanding of mechanism of impact of ID in human developing brain. It may also have important implications with regard to policy of interventions for different timing of ID, and improve children early development and the quality of population.