Ever since Meghan Markle and Prince Harry became engaged, the Duchess has become well known for her love of up-dos and messy buns.
But her new sister-in-law, the Duchess of Cambridge, on the other hand, has generally avoided wearing her hair up during her seven years as a royal family member.
Catherine is instead usually seen sporting her hair down, styled in her signature thick, glossy waves. And when she does wear it up, it's usually to accomodate a hat or a fascinator, for more formal events.
And it turns out, there may actually be an unexpected reason behind the Duchess' decision to wear her tresses down.
By wearing her hair down, the Duchess is actually concealing a rather large scar on the side of her head.
It sits on the left side of her head, just above her ear, and is easily visible if she pins her hair back away from her face.
Several years ago, Kensington Palace confirmed that the scar was actually the result of an operation Catherine had when she was younger.
They told ET, “The scar is related to a childhood operation." However, it's not known what kind of operation the Duchess had - whether it was medical or cosmetic.
However, we're sure that Catherine isn't altogether bothered about the small scar - and likely, simply prefers wearing her long locks down during royal engagements.
Duchess Meghan on the other hand has made it clear that she prefers popping her hair into a sleek up-do when on royal engagements.
But Catherine isn't the only royal with a noticable scar on their head.
Her husband, Prince William, has also joked many times in the past about the 'Harry Potter' scar he has on his forehead.
The Duke of Cambridge has revealed that his mark was actually brought about by a childhood accident, when he was hit in the head with a golf club at the age of 13. Ouch!
Catherine and William made a return to the public eye over the weekend, after a summer off from royal duties.
The couple were spotted attending a church service near to Balmoral Castle, where they and their three children are currently visiting the Queen and Prince Philip.
It's thought that the entire Cambridge family will be heading back to London in the next few days, before both Prince George and Princess Charlotte start back at school and nursery.
