I'm a big fan of the Olsen twin's slept-in-yet-super-chic beauty look, so when I found out they were sharing some of their best kept beauty secrets on Byrdie I may or may not have jumped for joy a little bit. While some of their tricks are somewhat obvious, others of them are a bit sneakier than I suspected!

For instance, their signature lip color? Turns out it's a lip liner! I would have never guessed. Mary Kate and Ashley are big fans of Make Up For Ever's Aqua Lip Liner in 3C.

When the twins want to jazz it up a bit, they then top that liner with Clinique's Chubby Stick in Heaping Hazelnut.

So simple yet so glam! For the full rundown of the Olsen's favorite beauty tips, tricks and products, click here! [via Byrdie]

Lovelies, do you ever use a lip liner as your lipstick?