This chapter concerns neuro-cognitive development, from conception through to childhood. Breastfeeding has been studied extensively using cross-sectional methods, finding cognitive benefits. However, after controlling for confounding variables and with better designs, beneficial effects are at best small. Maternal undernutrition can result in adverse neurodevelopmental outcomes (e.g., enhanced risk of schizophrenia). Undernutrition during infancy and early childhood causes stunting – inadequate growth for age. Stunting is common (around 500 million children worldwide) and is linked to multiple cognitive impairments, imposing lifelong costs on the individual. As stunting involves a complex interaction between nutrition, brain and environment, dietary remediation alone may not be that effective. Maternal overnutrition is also associated with adverse neurodevelopmental outcomes, but here it is unclear if this relates to poor diet quality, maternal body fat or socio-economic factors. Finally, there are a wide range of specific nutritional deficiencies that affect neurocognitive development, many having lifelong impacts (e.g., thiamine, folate iron, iodine).