It started with a simple sweater. After Harry Styles wore a color-block patchwork cardigan for the "Today Show" last February, knitters went into a kind of frenzy trying to reverse-engineer the pattern.

So many TikTok and YouTube users shared their process using the hashtag #harrystylescardigan — racking up tens of millions of views — that the creator of the original cardigan, Jonathan Anderson of the brand JW Anderson, released an official pattern and tutorial video.

In the end, the original sweater was acquired by the Victoria and Albert Museum in London, praised by the institution as a "cultural phenomenon that speaks to the power of creativity and social media in bringing people together in times of extreme adversity."

Knitters and crocheters always have been a resourceful (and community-minded) bunch. But the reverse-engineer-knitting craze unfolding on social media owes much to the current moment.

"Crafts bloom when people are stuck at home," said Abby Glassenberg, president and co-founder of Craft Industry Alliance.

The boon, Glassenberg said, is driven in part by crafters finding inspiration and encouragement from others. Patterns for scarves from "Harry Potter," shawls from "Little Women" and Baby Yoda plushies are easily found on Ravelry, a popular website by knitters and crocheters.

When Sen. Bernie Sanders was spotted (perhaps you've seen some memes?) wearing large patterned mittens to the inauguration, knitwear fans turned to Ravelry in search of the pattern. And sure enough, in less than 24 hours, Meg Harlan, a 27-year-old climate scientist, had reverse-engineered one and posted it to the site.

"I wrote the pattern to knit a pair for myself, sort of as a joke, but decided to post it as I love the community that Ravelry has created for sharing ideas and excitement about knitting/crocheting around the world," Harlan wrote in an e-mail. "It has been great fun to see all the comments from folks who are excited to be able to knit a pair for themselves!"

(The authentic Sanders mittens were made by Jen Ellis, a Vermont schoolteacher, who repurposed wool sweaters and then lined the mittens with fleece made from recycled plastic bottles.)

Reverse-engineered knitwear patterns are not necessarily designed for beginners. Caryn Shaffer spent months working out her pattern for the cream cable-knit sweater worn by Chris Evans in the 2019 movie "Knives Out."

"That movie is just full of really good knitting and knitwear," Shaffer said. "The Chris Evans sweater in particular was inspiring to a lot of knitters."

Pros get involved

Last summer, as TikTok explainers on how to reverse-engineer the Styles cardigan proliferated, Anderson knew he had to jump into the fray with his original pattern. He asked Ruth Herring, a knitwear designer and pattern author, to develop an official one.

"I really wanted to show our appreciation so we are sharing the pattern with everyone," Anderson said. "I liked the idea of something that felt authentic and almost homemade, like you or your grandmother could have made it, but at the same time, it feels quite deconstructed, quite punk."

Herring, 62, has worked with Anderson and the knitwear team at JW Anderson for several years but did not design the original cardigan worn by Styles. After she agreed to create the hand-knit pattern, the original cardigan was delivered for her to examine.

"The pattern is perfect for a beginner," she said. "You're starting with your basic stitches and then moving onto seed stitch and then color work."

Alas, crocheters who wanted to make the cardigan were left to work out converting the design on their own. In Los Angeles, Liv Huffman, 22, started working out her own crochet pattern for the cardigan. The two-week process, which Huffman, a social media influencer known for her makeup tutorials, posted to TikTok, was so popular that Huffman's creation will join the JW Anderson design at the Victoria and Albert Museum.

Shaffer is also seeing intense interest in her "Knives Out"-inspired pattern. She started the pattern after seeing the film in December 2019 but didn't work on it in earnest until being furloughed during the spring. She worked out the pattern in a Google Doc, a public document that allowed other knitters to follow along as she analyzed how to form the sweater's unique cables.

"I made the pattern for free because I want as many people to be able to access knitting for themselves and find the same comfort in it that I have over the years," Shaffer said.

Slowing down

There are endless ways to customize a piece of knitwear, which is part of the appeal for many makers. Herring and Shaffer said they have heard from other crafters who are putting their own spin on the patterns by changing the weight or color of the yarn.

With so many first-time knitters starting during the pandemic, though, Herring said she worries about the sustainability of the materials being used. Many first-time crafters choose a cheaper synthetic yarn, but Herring suggests choosing a natural fiber yarn that will last longer.

Knitting or crocheting a garment is far from the quickest way to have a finished product. Manufactured knitwear abounds, but hand-making a cardigan, hat or scarf is a slow and meditative process (and has been for thousands of years). Slowing down and watching a project grow stitch by stitch — however imperfectly — is deeply satisfying.

"Knitting is confidence-building," Herring said. "Starting with two sticks and a bit of string or a crochet hook, you can create something beautiful."