A newborn is a baby in the first 28 days of life, the neonatal period, when the infant adapts from the womb to independent breathing, feeding, and temperature regulation. From a nutrition standpoint, this is the most critical feeding window: exclusive breastfeeding is recommended for the first six months, with colostrum in the first days providing concentrated antibodies, growth factors, and easily digested nutrients. Where breastfeeding is not possible, infant formula manufactured to strict compositional standards provides the alternative. Newborns have immature kidneys and gut barriers, which is why water, honey, and cow’s milk are unsuitable in early infancy, and why vitamin K is given at birth and vitamin D supplementation is advised in many countries. Weight, feeding, and jaundice are monitored closely throughout the period.