It's a bit like a biological USB port,

transferring oxygen and nutrients to you in the womb.

And although you probably don't pay it much attention

it's key to what makes us human -

in fact it's just about impossible to be born without one.

Omphalophobics beware, we're talking about belly buttons.

Available in two varieties, innie or outie,

nearly every mammal has a belly button.

I said nearly, I'm looking at you duck-billed platypus -

we'd need a whole other video for what you've got going on.

Now not having easy access to scissors,

other mammals tend to just gnaw their umbilical cords off

after they're born

and therefore they have flatter scars that are more difficult to see.

Now even if we humans didn't snip our umbilical cord

it would just go a bit dried and horrible

and fall off after three to 10 days anyway.

Some celebrities have even kept the withered remains

and used it to make art - which is, you know, very normal and fine.

The humble belly button

is one of the first things about you that develops in the womb,

way before the brain or the lungs or anything, really.

It's the very foundation of what you are.

It connects directly to your umbilical cord

which is made up of a vein and two arteries.

The umbilical cord keeps us alive in the womb -

a squishy motorway carrying oxygen and nutrients

from the placenta to the foetus

and transporting waste products back the other way.

That cord is the most indispensable but disposable organ

you're ever going to have.

It's a key part of what makes us mammals too.

The connection with our mothers before we're born

is integral to our development.

Your mother's belly button probably changed as you grew inside her too.

Many expectant mums go from having an innie to an outie

in the second or third trimester of pregnancy.

When their expanding uterus puts enough pressure on the abdominal wall

pop goes the navel.

Once you've made your grand entrance into the world

it may seem like your belly button has served its purpose

but it does remain important,

especially if you ever need abdominal keyhole surgery.

The belly button is the ideal entry point,

being so central to all your vitals.

The navel has fascinated various cultures throughout history,

from Greek myths suggesting our scars are a reminder from the gods

not to have another go at an uprising.

"Can't go to war sorry, my belly button says so."

To Japan, where children are warned that during a storm

the demonic, three-fingered god of lightning, Raijin,

could steal their belly buttons

in the seconds after a lightning flash. Scary.

Although we all have them, subject to Raijin's mercy,

belly buttons were taboo until fairly recently.

Not so long ago, they were deemed too hot for TV in the US

and were banned from appearing on screen in 1934.

By the 50s, female stars were skirting the line

of so-called decency

by covering their navels with jewellery so they could belly dance

without causing too much of a fuss.

Nobody seems to be able to agree on

who was the first to slip by the American censors.

Some say it was Star Trek,

going boldly where no TV show had gone before in 1967.

While some others claim it was Cher herself

who first showed her navel on the telly,

but to clear that one up, we might have to 'Turn Back Time'.

The next logical step for belly button enthusiasts is of course...

making belly button cheese.

Turns out that the unique bacteria nestled in some navels

can actually be used in cheesemaking,

leading to what might be the weirdest brie you're likely to never sample.

Right, OK, that's enough about belly button cheese.

Whether you end up with an innie or an outie

has nothing to do with how the umbilical cord is cut.

It's just part of what makes us diverse.

So whatever you've got,

dig out that crop top from the back of the wardrobe

and wear it with pride.

Now let's face it, they're not much to look at

but they've fascinated us since we first gazed upon our own navel

confronted with the knowledge that we once had

a literal, physical connection with another person.

So take a minute to ponder the humble belly button.

And get that bit of fluff out of there while you're at it.