The next time you look in the mirror.

think about this.

In many ways,

you're more microbe than human.

There are ten times more cells

from microorganisms -

bacteria, viruses, fungi-

than human cells in and on our bodies.

And our genes are outnumbered

a hundred to one by microbial genes.

Scientists even have a name

for all these microbial genes:

the human microbiome.

Now, this might make a lot of people

rush for the hand sanitizer,

but it turns out most

of these microorganisms aren't bad,

germs that will make us sick,

most are good.

And without these good microbes

our bodies don't seem to do as well.

We don't seem to be as healthy,

and we actually might get sick

more often.

So one question is:

where do our microbiomes

come from in the first place?

Well, like a lot of things,

it starts with our mothers.

As the infant passes 
through the birth cannal,

it gets coded with microbes from the mom.

These microbes may kind of

seed the baby with just the right mix.

Combined with bacteria in breast milk

and other microbes we encounter early on,

they seem to slowly take shape

in our first few years of life.

The overall mix of our microbes

becomes very personal,

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

But our microbes tend to resemble

those of our parents and siblings.

And may stay with us 
for much of our lives.

They may also be doing 
all sorts of things,

such as educating our immune cells,

like this one.

Teaching them the difference

between things they should fight off

–bad bugs that might make us sick-

And things that aren't a threat,

like our good microbes.

When we are adults,

microbes become our first line of defense,

fighting off germs that try to invade our

bodies, protecting their

turf, while protecting our health.

Scientists have discovered they can

even spew out their own antibiotics.

The types of microbes in your body

vary depending exactly where they live,

like different ecosystems in nature.

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

Oily places, like our scalps and backs.

And dry places, like our forearms.

Different species of microbes

have adapted to each of these habitats.

The biggest, most important 
microbial habitat

seems to be in the gut.

It's the most complex, the most diverse,

and everything microbes are doing

everywhere else in our bodies:

fighting off infections,

revving up and dampening down 
our immune systems,

signaling cells...

That's all happening 
in the gut in spades.

They even seem to help 
regulate our metabolisms.

How much energy we burn,

and how much fat we store.

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

because of what we eat, 
antibiotics we take,

that may actually lead 
to all kinds of diseases.

Diseases like colon cancer, colitis,

maybe even diabetes
and obesity.

Some scientists think one reason

a lot of diseases are increasing

is because we've lost key gut microbes.

Our microbiomes look far 
less diverse compared to those

compared to those of people

in less developed countries 
and earlier generations.

And remember how we get

our microbiomes in the first place?

From our mothers when we are born,

and from breast milk?

Well, some scientists think that

too many babies aren't getting that,

because of all the C-sections,

and not enough breast feeding,

plus all the antibiotics 
kids get these days,

and our obsession with cleanliness.

All this may help explain why problems

like asthma and allergies,
have been soaring

Maybe because our microbiomes

never taught our immune systems

how to work the right way.

Maybe swallowing good microbes probiotics

could prevent and treat some diseases.

So could taking prebiotics

essentially food that good microbes love.

We end our story with a reminder.

This research is really new,

we still have a lot to learn

about what many of our microbes

are really doing.

But scientists say that

it's getting clearer and clearer that

the tiny organisms all over our bodies

are essential to our health and happiness.