The prenatal and early postnatal periods constitute a time of rapid development when the brain is in a state of both heightened plasticity and vulnerability. Premature infants and infants of diabetic mothers represent two experiments of nature that allow researchers to observe how the developing brain responds to early biological challenge of either a global or regionally specific nature. We outline a set of organizing principles for conceptualizing the mechanisms by which early adverse experience may be encoded in the brain and subsequently expressed in behavior. We then review the available literature on developmental outcomes for infants born premature and infants of diabetic mothers. Research examining the relative influence of experience and maturation in the development of preterm infants indicates that advance experience does not accelerate the advent of specific cognitive capacities, but may enhance performance once the particular ability has emerged. Long-term follow-up of preterm infants also reveals evidence for plasticity and cognitive improvement into early adolescence for later maturing executive functions. Finally we offer an integrated model for investigating cognitive outcomes in infants of diabetic mothers that incorporates data from animal, electrophysiological, and behavioral measures.