We've considered the Olsen twins style icons for as long as we can remember. Yes, even in their To Grandmother's House We Go days, Mary-Kate and Ashley have been setting our #SquadOutfitGoals. They've since grown up and ditched the whole same-outfit-in-different-colors shtick. Nowadays, they prefer luxe staples that reflect not only their individual personalities, but also the sophistication of their adult gig: CFDA Award-winning fashion designers.Today, the duo turns 30. So, to fete the Olsens, we're looking back at Mary-Kate and Ashley's street style. Celebrate some of their most memorable fashion lessons, like how wearing all-black is still the epitome of chic, how layering can be cool and not miserable, and why comfortable footwear is the way to go (unless your pumps have sparkles on them). Their last and most important lesson, though, cannot be overlooked: how it's physically impossible to look underdressed when draped in Elizabeth and James and The Row.This is by no means a new exercise for us, so, we'll continue doing what we've been doing for years: stalking Mary-Kate and Ashley's style to discover how to be them.