From Birth, Our Microbes Become As Personal As A Fingerprint

Look in the mirror and you won't see your microbiome. But it's there with you from the day you are born. Over time, those bacteria, viruses and fungi multiply until they outnumber your own cells 10 to 1.

As babies, the microbes may teach our immune systems how to fight off bad bugs that make us sick and ignore things that aren't a threat.

We get our first dose of microbes from our mothers, both in the birth canal and in breast milk. Family members tend to have similar microbiomes.

"The mother's microbiome has actually poised itself over nine months to basically become the prime source of microbes to the infant," says Lita Proctor, director of the Human Microbiome Project at the National Institutes of Health.