This prospective observational study aims to identify and characterize immunoregulatory microRNAs (miRNAs) associated with regulatory T cells (Tregs) in human breast milk and to evaluate their temporal expression patterns. Breast milk samples will be collected longitudinally, including colostrum, transitional milk (days 10-15), and mature milk at 1, 4, 6, and/or 9 months postpartum. The study will investigate miRNAs that may influence the development and function of Treg cells and assess changes in their expression over time. In addition, a single blood sample will be obtained from infants during routine clinical visits (6-9 months postpartum) to analyze Treg-related miRNAs and target genes and to evaluate their relationship with breast milk components. The study also aims to explore the association between breast milk miRNAs, Treg-related immune mechanisms, and the development of infant food tolerance.