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The next time you look in the mirror.

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think about this.

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In many ways,

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you're more microbe than human.

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There are ten times more cells

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from microorganisms -

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bacteria, viruses, fungi-

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than human cells in and on our bodies.

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And our genes are outnumbered

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a hundred to one by microbial genes.

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Scientists even have a name

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for all these microbial genes:

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the human microbiome.

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Now, this might make a lot of people

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rush for the hand sanitizer,

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but it turns out most

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of these microorganisms aren't bad,

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germs that will make us sick,

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most are good.

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And without these good microbes

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our bodies don't seem to do as well.

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We don't seem to be as healthy,

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and we actually might get sick

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more often.

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So one question is:

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where do our microbiomes

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come from in the first place?

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Well, like a lot of things,

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it starts with our mothers.

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As the infant passes 
through the birth cannal,

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it gets coded with microbes from the mom.

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These microbes may kind of

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seed the baby with just the right mix.

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Combined with bacteria in breast milk

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and other microbes we encounter early on,

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they seem to slowly take shape

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in our first few years of life.

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The overall mix of our microbes

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becomes very personal,

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sort of like a fingerprint, 
or maybe a blood type.

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But our microbes tend to resemble

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those of our parents and siblings.

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And may stay with us 
for much of our lives.

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They may also be doing 
all sorts of things,

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such as educating our immune cells,

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like this one.

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Teaching them the difference

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between things they should fight off

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–bad bugs that might make us sick-

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And things that aren't a threat,

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like our good microbes.

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When we are adults,

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microbes become our first line of defense,

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fighting off germs that try to invade our

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bodies, protecting their

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turf, while protecting our health.

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Scientists have discovered they can

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even spew out their own antibiotics.

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The types of microbes in your body

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vary depending exactly where they live,

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like different ecosystems in nature.

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There are wet places, like
our mouths, noses and armpits.

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Oily places, like our scalps and backs.

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And dry places, like our forearms.

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Different species of microbes

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have adapted to each of these habitats.

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The biggest, most important 
microbial habitat

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seems to be in the gut.

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It's the most complex, the most diverse,

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and everything microbes are doing

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everywhere else in our bodies:

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fighting off infections,

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revving up and dampening down 
our immune systems,

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signaling cells...

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That's all happening 
in the gut in spades.

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They even seem to help 
regulate our metabolisms.

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How much energy we burn,

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and how much fat we store.

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So, if it's not functioning properly 
for some reason

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because of what we eat, 
antibiotics we take,

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that may actually lead 
to all kinds of diseases.

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Diseases like colon cancer, colitis,

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maybe even diabetes
and obesity.

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Some scientists think one reason

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a lot of diseases are increasing

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is because we've lost key gut microbes.

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Our microbiomes look far 
less diverse compared to those

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compared to those of people

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in less developed countries 
and earlier generations.

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And remember how we get

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our microbiomes in the first place?

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From our mothers when we are born,

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and from breast milk?

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Well, some scientists think that

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too many babies aren't getting that,

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because of all the C-sections,

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and not enough breast feeding,

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plus all the antibiotics 
kids get these days,

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and our obsession with cleanliness.

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All this may help explain why problems

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like asthma and allergies,
have been soaring

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Maybe because our microbiomes

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never taught our immune systems

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how to work the right way.

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Maybe swallowing good microbes probiotics

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could prevent and treat some diseases.

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So could taking prebiotics

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essentially food that good microbes love.

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We end our story with a reminder.

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This research is really new,

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we still have a lot to learn

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about what many of our microbes

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are really doing.

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But scientists say that

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it's getting clearer and clearer that

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the tiny organisms all over our bodies

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are essential to our health and happiness.