If you grew up in the 90s, odds are you desperately tried to tell the Olsen twins apart on Full House, but failed miserably.

Well, what if we told you there was a surefire way to tell the difference between Mary-Kate and Ashley — and you've been missing out on this incredible knowledge for decades?

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It's funny how when people discuss the physical differences between the two, they point out how Mary-Kate is left-handed and Ashley is right-handed, which clearly does not help anyone in telling them apart (unless they're playing ring toss of course).

What they fail to mention is that the girls' eyes are completely different shapes — and Ashley's are much closer together than Mary-Kate's. Let's have a look, shall we?

Here's Ashley. Notice how round and closer together her eyes are?

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Now here's Mary-Kate. Her eyes are more spaced out and not as round.

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Let's try this again … Ashley.

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Aaaaaand Mary-Kate.

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There you have it folks, you're welcome. Now go off and share this newfound information with your friends.

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(Clearly, that's Mary-Kate.)