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A human’s genes are laid down at
conception. A fetus’ heart, brain and other organs start to form five weeks later.
At six months, an unborn child has most of its body parts. But there is one
essential component missing: the helpful bacteria, often referred to as the microbiome,
that will inhabit its gut, skin and other organs.

Our first interactions with microbes set the stage for health throughout our lives. Babies’ microbiomes have been linked to hea