Back in March, while promoting Wuthering Heights, Margot Robbie touched down in Sydney, Australia, in what looked like the simplest outfit imaginable: an oversized black long-sleeve tee, , and . Yet somehow that combination has quietly launched a thousand style ships. Ever since, I've been spotting versions of it everywhere: the sort of outfit that looks as though you threw it on without a second thought, despite the fact that getting it right is actually quite precise. The key? Proportion. The . The . The sleeves need to hit at exactly the right spot. Miss by an inch and you're heading toward pajamas. Get it right and suddenly you look throw-on-and-fly way that seems impossible to explain. The easy-to-pull off takeaway here is the long-sleeve T-shirt though. Think of it as this summer’s version of the ubiquitous unbuttoned button-down. Proof below. The best spot-on options currently come from (and in s too), (perfection), , and .