Inclusion Criteria:  Full-term (more than 37 weeks and >2.5kg) Children aged between 1.5-6 months (42-182 days) or 9-15 months (274-456 days) at enrolment. Normally developing infants and toddlers as assessed by clinician. No major risk factors for learning, neurologic, or psychiatric disorder as assessed by clinician. Baseline dietary pattern in the past 60 days and intention to continue current dietary pattern during course of the study in one of three groups below:  I. Predominantly breast-fed group II. Predominantly infant formula-fed group III. Follow-Up Formula / Growing Up Milk-fed group  Exclusion Criteria:  History of diagnosed neurological (e.g., head injury, epilepsy), psychiatric or developmental disorder in parents or siblings, as assessed by clinician. In-utero exposure to alcohol abuse or illicit substances as defined as diagnosis of current substance use disorder in the biological mother and guidelines set by the American College of Obstetricians and Gynecologists and the Royal College of Physicians. Multiple birth as reported in medical record. Abnormalities on fetal ultrasound as reported in the medical record (outpatient obstetrics medical records). Complicated pregnancy (e.g., preeclampsia, gestational diabetes) as assessed by medical interview/ medical record. Neonatal intensive care unit admission (>24h) and/or emergency surgical delivery as reported in medical record. Abnormal screening laboratory values and studies considered to be clinically significant in the opinion of the Investigator (e.g., metabolic disease screening, neonatal bilirubin).