Preterm infants, born before 37 wks of gestation, require specialized nutrition to support catch-up growth and minimize metabolic risks. This review compares key enteral nutrition sources-breast milk, fortified breast milk, and preterm infant formula-highlighting their compositional differences and effects on growth and development. It emphasizes the importance of mimicking human milk components, particularly lipids, proteins, and oligosaccharides, to enhance feeding outcomes and gut microbiota development, and explores recent advancements in formula optimization. Personalized nutrition strategies, considering intake volume, breast milk composition, the components of human milk fortifiers, and the safety of mixed nutritional supplements, are essential. Emerging technologies, including encapsulation, the regulatory approval of novel ingredients, and AI-driven tools, offer new possibilities for improving nutritional outcomes in preterm infants.