To induce weight gain, 100-120kcal/kg in term neonate and 110-140kcal/kg in preterm are needed. Vitamin and mineral requirement for preterm are not clearly established. Caution is required with vitamin supplementation, because toxicity may occur with both water and fat soluble vitamins as a result of immature renal and hepatic function. Iron deficiency associated with short-term and long-term neurodevelopmental deficits, delayed maturation of the auditory brainstem responses, and abnormalities of memory and behavier. Preterm infants are more susceptible to iron deficiency due to small iron stores at birth, high velocity, and phelebotomy loss. Term healthy infants should be breast fed as soon as possible within the first hour. The following criteria should usually be met before initiating infant feeding: 1-absence of excessive oral secretion, 2- nondistended, soft abdomen with normal bowel sounds, 3- respiratory rate<60, 4-prematurity. Feeding cautions: should also be extended to term infant with perinatal depression, polycythemia and congenital heart disease who are also at risk of developing NEC. Human milk is preferred for feeding term, preterm, and sick infant.Feeding intolerance: presence of bilious aspirates, emesis, blood in stool, abdominal distention or other systemic signs such as apnea and bradycardia should be closely evaluated.