Seeding is the process by which a baby is first colonized by her mother’s beneficial bacteria. When a baby emerges through the birth canal, she is colonized by the beneficial microbes that reside there, and those microbes begin to lay the foundation for her gastrointestinal and immune system. This process of seeding continues through skin-to-skin contact, breastfeeding, and eventually, interactions with the surrounding environment. Up until the first 5 years of life, the microbes stabilize into what is called the 'steady-state' microbiome, resembling more or less that of an adult microbiome.

The majority of these bacteria and microbes reside in the gut. But beyond the gastrointestinal tract, there are also communities of vastly different species in the nose, the groin, and on the skin. Some microbes prefer to live on the cool, dry skin of the knee. Others gravitate towards the warm, wet darkness of the mouth. They are tiny ecosystems as different from each other as the rainforest and the desert. Wherever they live, they’ve evolved to thrive there.