If you've seen people in the wild, or more likely on Instagram, wearing two T-shirts - yes, two - you're not imagining things (Joey Tribbani clearly had the right idea all along).
Sometimes it's subtle - a kind of IYKYK. Stylist Marianne Smyth, for example, simply tucked one round-neck under another - Bassike's cult striped crew was her basic-yet-chic outer layer - leaving the merest hint of green at the hem.
Other times it's very much intentional, a styling flex that's most likely trickled down from Miu Miu, whose street-style posse really pioneered the double-tee trick at Paris Fashion Week. Influencer Livia Nunes Marques wore two short-sleeved polo shirts under a zippered sports top, creating a triple-collar effect in coordinated primary colours.
Janka Polliani, the consultant, stylist and podcast host, stuck with two layers, but mixed up the mediums ever so slightly, with a striped button-down tucked underneath an oversized and long-sleeved Breton. It was a sporty take on the preppy trend that looked especially cute with a drawstring mini but would also work as the top half to tracksuit bottoms or a pleated midi skirt.
On SS Daley's SS25 catwalk, meanwhile, one model wore two popped-collar shirts buttoned one over the other. Styled with flower-power culottes, black ankle socks and patent courts, it was a twist on boardroom dressing that would definitely shake up your office rotation.
The best thing about this styling trend, of course, is that it doesn't involve any shopping. My suggestion would be to pull out all your tees, shirts and long-sleeved tops that have the potential to be layered for an old-fashioned trying on 'sesh'. For a bit of entry-level styling, try popping one tee over another, preferably in contrasting shades, rolling up the sleeves a little to make things a bit more obvious. Once you've mastered that move, you can upgrade to double polo shirts, button-downs under Bretons, and - not for the faint-hearted - a boob tube over a classic white shirt.
Natalie Hammond is Grazia’s Senior Fashion News Editor. She loves winter, hates summer and can often be found writing about the weather (and what on earth to wear).