Travel Guides twins Stack and Mel thought they were identical - until they discovered one bizarre difference

Former Travel Guides stars Stack and Mel are familiar faces on TV, but just how similar are their faces?

In the search for the country's most alike set of twins in a captivating new series, Australia's Most Identical, the celebrity sisters set out to find the answer.

Using 3D facial scanning technology, one bizarre difference between the twin sisters left them absolutely stunned.

See the incredible results in the video above.

Stream episodes of Australia's Most Identical for free on 9Now.

Humans have more than 20,000 genes and in identical twins, these genes are exactly the same.

But what explains the slight difference in appearances?

EXCLUSIVE: Travel Guides stars Stack and Mel reveal what they've been up to since leaving the show – from motherhood to the rodeo

In this gripping special event series, Stacey and Mel Wilburn (better known as Stack and Mel) confirmed how closely matched they really are:

They called in a 3D scanning engineer to measure the differences in the twins' faces right down to the millimetre.

Overlaying the two face scans, the engineer used facial recognition technology to compare the pair.

Everything in green is a match within a millimetre.

"That's amazing," marveled Mel.

But while the girls are very close, it was revealed Stack's ear was four millimetres out when compared to Mel!

READ MORE: Identical twin reveals secret she kept from sister for 10 years - live on air

"Four millimeters?!" Mel laughed stunned. "You could fly away with them."

READ MORE: Everything you need to know about Australia's Most Identical

According to experts in the series, identical twins don't always have identical experiences in the womb, which can result in physical differences.

Now that's one difference the sisters didn't expect to find!

Australia's Most Identical continues Wednesday night at 7:30pm on Channel 9 and 9Now.

Catch some of the most fascinating moments from Australia's Most Identical here:

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