It's 8 a.m. on a recent day at Forward Operating Base Nolay, a small Marine outpost in Taliban-infested Sangin District of southern Afghanistan's Helmand province. The Marines are in the process of caffeinating and preparing for the day.
Suddenly, explosions and gunfire ring out. The Marines don't run for their weapons or bunkers for that matter. They don't even flinch.
"We can sit here and we can have a cup of coffee when there's booms going on, we're not concerned about it," says Lt. Col. Jonathan Loney.
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.