The aim of the study is to establish the longitudinal microbiome and bone trajectories from birth to 3 years, and to evaluate the influence of nutrition on these trajectories.

The main objective of the study is to understand the influence of nutrition and dietary patterns on microbiome and bone trajectories during early life. Specific research objectives are:

• Establish the reference trajectories of gut microbiome maturation index and bone development in healthy Chinese children aged 0-3years
• Assess the impact of early life nutrition on gut microbiome trajectory
• Investigate the influence of microbiome, early life parameters and nutritional parameters on bone health

Inclusion Criteria:

• It is important to carefully consider whether a subject is suitable for enrollment into this observational study. Fulfillment of the inclusion and exclusion criteria for each subject will be documented by a qualified member of the investigative staff before any subject is enrolled.

Healthy infants who fulfill all the following inclusion criteria will be included:

1. Having obtained his/her parents' (or his/her legally accepted representative's [LAR's]) written informed consent and having evidence of personally signed and dated informed consent document indicating that the subject's parents/LAR have been informed of all pertinent aspects of the study.

2. Subject's parent(s)/LAR is of legal age of consent, is willing and able to fulfill the requirements of the study protocol.

3. For group 1, healthy infants aged ≤ 10 days after birth (date of birth = Day 0).

   For group 2, healthy infants with maximum age of 6 months

4. Full-term gestational birth (≥ 37 and ≤ 42 weeks).

5. Subject's parent(s)/LAR is able to be contacted directly by telephone throughout the study.

6. Both parents registered have a fixed work and / or residence within their jurisdiction.

Exclusion Criteria:

1. Complicated pregnancy (e.g., preeclampsia, gestational diabetes, bowel disease) as assessed by medical interview/ medical record when available
2. Infant's parents/LAR not willing and/or not able to comply with scheduled visits and the requirements of the study protocol
3. Currently participating or having participated in another clinical trial within 4 weeks prior to trial start.

Group 1: 690 healthy infants and their mother followed from birth to 12 months Group 2: 690 healthy infants and their mother followed from 6 months to 3 years of age