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The earliest iteration of fleece was pile, the fluffy, sheep-like stuff that’s now considered retro enough to be trendy again.

“Won’t shrink, pull out of shape or pill; lightweight, quick-drying, very warm, ideal for layering.” This description appeared alongside Patagonia’s Synchilla fleece in the late ’80s. Today, fleece is taken for granted — it’s commonplace, a noun that refers to both material and article of clothing. But for its prevalence, fleece is surprisingly young. The synthetic polyester fabric was introduced in 1981 as the result of a collaboration between Massachusetts-based Malden Mills, now known as Polartec, and Patagonia.

Fleece didn’t emerge fully formed, though. Patagonia’s earliest experiments were made with a bulky pile that often pilled. It wasn’t until 1985 that Patagonia and Malden Mills landed on Synchilla, the double-faced, non-pilling fabric introduced in the Snap-T pullover, a staple in Patagonia’s collection to this day. It took less than a decade for Synchilla to catch on as brand-name fleece, and despite Patagonia’s efforts to market this new type of apparel as technical mountain wear, it flowed into the everyday and fashion domains, too.

But it isn’t this newer iteration of fleece that’s currently having a moment; it’s pile. Yes, the fluffy, sheep-like stuff that was once considered deficient is now coming back into style. Also known as shearling fleece or sherpa fleece, pile has been vastly improved upon, but in many cases, it’s still made and worn as everyday apparel. This tendency is in no small part a result of an increased interest in retro-outdoor aesthetics inside the industry and beyond.

Mainstay outdoor companies like Patagonia and Rab have recognized and capitalized on the trend with the throwback positioned as the main draw, but pile fleece can be technical too. Burton used it as the foundational material in its Minturn fleece, a functional layer designed for snowboarding, and won Polartec’s Apex Award for fabric innovation. “We selected the Polartec sherpa fleece because it provides warmth and a unique look, but it’s still breathable and functional,” says Charlie VanDerlip, Senior Global Merchandiser at Burton. “Sherpa has historically come and gone with trend, but recently it seems to have become more of a staple. If you use a high-quality sherpa fleece, it will hold up over time, and perform really well as a mid-layer for warmth.”

Lifestyle clothing rooted in the heritage and tradition of the outdoors certainly isn’t going anywhere anytime soon, so it’s likely that pile is here to stay too.