The purpose of this study is to investigate the associations between human milk nutrients and infants' health outcomes in China.

Human milk components are beneficial to the growth and development of infants, such as phospholipids, gangliosides, sialic acids, choline, oligosaccharide and so on. However, studies on the associations between human milk components and infants' outcomes are limited. Therefore, this study is designed to investigate the relationship between Chinese human milk components and the growth and development of infants.

Inclusion Criteria:

• age 4-5 years
• healthy children
• breastfeeding between 0 to 400 days of age
• human milk components in human milk being determined
• sign informed consent

Exclusion Criteria:

• children with severe chronic diseases, such as tumor, severe digestive diseases, kidney diseases
• gestational diabetes, hypertension and other metabolic diseases
• children with mental system diseases
• children with congenital and genetic diseases
• children with infectious diseases, eg, upper respiratory tract infection or diarrhea
• antibiotic or other drugs influencing intestinal flora being taken within 45 days
• Withdraw withdraw informed consent serious violation of the scheme no longer meet the research criteria because of health factors or accidents

Children of this study will be recruited from lactating women provided human milk samples before.