Inclusion Criteria:
1. Written informed consent is obtained from parent(s)/ legally authorized representative(s) (LAR(s)).
2. Parent(s)/ LAR(s) must be able to provide evidence of parental authority and identity.
3. Parents/ LARs must understand the informed consent and other study documents.
4. Infants whose parent(s)/ LAR (s) has consented to blood collection as per protocol.
5. Able to temporarily store stool samples in a household freezer.
6. Infants whose parent(s)/LAR(s) are willing and able to comply with scheduled visits, and the requirements of the study protocol.
7. Infants whose parent(s)/LAR(s) can be contacted directly by telephone throughout the study.
8. Infants must meet all the following inclusion criteria to be eligible for enrollment into the study:
1. Healthy term infant (≥37 weeks of gestation)
2. At enrollment visit, postnatal age ≥14 to ≤35 days (date of birth = day 0)
3. Birth weight is appropriate for gestational age (i.e., ≥ 2500g and ≤ 4500g)
4. Infant has exclusively received breastmilk from birth to enrollment, and parent intends to continue exclusive breastmilk feeding until infant age 6 months.
Exclusion Criteria:
1. A medical condition or history that could increase the risk associated with study participation or interfere with the interpretation of study results, including:
1. Evidence of major congenital malformations (e.g., cleft palate, extremity malformation).
2. Suspected or documented systemic or congenital infections (e.g., human immunodeficiency virus, cytomegalovirus, syphilis).
3. Previous or ongoing severe medical or laboratory abnormality (acute or chronic) which, in the judgment of the investigator, would make the infant inappropriate for entry into the study. Of note, children who are normally healthy but at the time of enrolment suffering from acute illness in a minor condition which are common in childhood and do not require some of the exclusionary medication mentioned below can be enrolled.
2. Presently receiving or have received prior to enrolment any of the following: medication(s) or supplement(s) which are known or suspected to affect the following: fat digestion, absorption, and/or metabolism (e.g., pancreatic enzymes); stool microbiota and characteristics (e.g., oral, or systemic antibiotics, glycerin suppositories, bismuth-containing medications, docusate, Maltsupex, or lactulose); growth (e.g., insulin or growth hormone); gastric acid secretion.
3. Infants whose parent(s) has(ve) not reached legal age of majority (18 years old) upon enrollment.
4. Currently participating or having participated in any interventional clinical trials since birth.
