They've evolved to be round

so that they can swivel to spot delicious prey

and easily roll when your cousin

talks about his new car for the third time.

But to get to that point, our peepers have come a long way.

They most likely developed from a tiny light-sensitive patch

on single-celled organisms that would help them move towards light

in the hope of finding food.

As the creatures evolved, this patch started to curve inward

to better focus light. And now, a whole bunch of evolution later,

what we've arrived at are two twinkling spheres

that are capable of seeing about a million colours.

Not bad, eh?

We might actually be on to something with that

'window to the soul' stuff too,

as our eyes can portray more about our emotions than you might think.

Your pupils dilate when you're scared, nervous or excited.

That could be why they enlarge when we make eye contact

with someone we, like, like-like.

Research has also shown that even making eye contact with

a portrait painting sets off a whole raft of brain activity.

Our eyes are also responsible for another universal emotional reaction

- a good old weep.

But we actually have three types of tears,

each with their own chemical makeup.

Basal, which lubricate the eye.

Reflex tears, caused by irritants like dust or chopped onions.

And psychic, or emotional tears,

the kind that appear when you find out about Bambi's mum

for the first time.

When it comes to our pupils, it's not just the size of them that varies -

the shape of an animal's pupils can tell us if it's predator or prey.

Some have horizonal pupils, making them more adept at scanning

for predators while munching on grass...

found on your local goats, sheep, and moose.

Vertical pupils like those found on foxes, cats and crocodiles

are better for ambushing and hunting at night, and have become synonymous

with animals that you just do not want to mess with.

Our round pupils are kind of a best of both worlds

and help us in active foraging and chasing down prey.

Which, you know, we totally do, all the time.

There are quite a few animals who do a better job of seeing than we do.

The elephant hawk-moth,

which sounds like that band your dad might have been in,

was the first animal proven to be able to see colour

in the dead of night.

Their large, sensitive eyes allow the maximum

available light to pass through.

However, this does impact their ability to detect fast-moving objects

like a rolled-up newspaper.

Human eyes might not be perfect. Parts of them are even useless,

like that little pink bit in the inner corners. \N

That's the remains of a third eyelid

like the ones cats, dogs and camels have.

Our eyes aren't just physically interesting, but culturally too.

Much loved by conspiracy theorists the world over, The Eye of Horus

may symbolise the Illuminati to some, but its origins lie in Egypt

where the eye is a symbol representing sacrifice,

healing and protection.

In Turkey, some believe that a sideways glance can cause

genuine pain. And thinking back to high school,

they're not wrong.

Glass pendants, also eye-shaped, are worn to protect

against this evil eye.

So whether round, monolid, hooded, downturned, upturned or almond,

words you're probably familiar with if you spend as much time watching

makeup tutorials as me, your eyes are unique to you.

The two are even unique to each other.

But one thing does unite us all...

we can't for the life of us keep them open when we sneeze.