Benefits of breastfeeding are widely recognized, during the last decades human milk has been identified as the normative standard for infant feeding and nutrition. Recent evidence focused on specific bioactive and immunomodulatory factors, such as oligosaccharides, lactose, glycosaminoglycans of human milk and the variability of their concentrations during lactation in both term and preterm milk. Human milk should be fortified with proteins, minerals and vitamins to ensure optimal nutrient intake for preterm VLBWI infants. Best fortification strategies as well as the optimal composition of fortifiers are still object of research. Short and long-term clinical, metabolic, immunologic and neurodevelopmental advantages of breastfeeding ndividualizes fortification - particulary adjustable fortification- has proven to be effective when compared to formula are well documented. Moreover several non-experimental studies observed that clinical feeding tolerance is improved and the attainment of full enteral feeding is quicker by a diet of human milk. In addition, benefits of breastfeeding on psychological and relational aspects have to be considered. Mothers own milk remains the first choice for all neonates, when it is not available or not sufficient despite significant lactation support, donor milk represents the second best alternative and although some nutritional elements are inactivated by the pasteurization process, it still has documented advantages compared to formula.