The breast milk has a composition which varies depending on a multitude of factors; these variations adapt perfectly to the infant’s needs. Among the main nutrients, lipid concentration suffers most of the changes, especially 30 minutes after breastfeeding. The theory of fat globule adsorption to the mammary alveolar membrane is more considered a biological response than a physical one and reflects the physiological changes associated to milk secretion. The breast milk is a dynamic product, with macronutrients, micronutrients, bioactive factors, absolutely indispensable for the newborn and infant growth.