The administration of the adequate amount of nutrients helps to improve a correct short-term linear growth and long-term neurocognitive development. To reduce the extra-uterine growth delay in very low birth weight infants (VLBW) the best strategy of nutrition (parenteral or enteral) should be established rapidly, since the first day of life. In preterm infants, nutrition can be administered parenterally and enterally. Prematurity is the most frequent indication for parenteral nutritional support due to intestinal functional immune deficiency, deficiency of digestive enzymatic systems and reduced nutritional reserve of these infants. In terms of enteral nutrition, breast milk is the first choice. In case of preterm and VLBW infants, fortifiers are used to overcome breast milk's protein and mineral deficiencies. When breast milk is not available, specific infant formula is the alternative.