Taylor Swift broke up with Harry Styles earlier in January and the 23-year-old began working on a breakup ballad inspired by the One Direction singer ever since, according to The Sun. 

A source said the "I Knew You Were Trouble" singer has been working on a song about her split since she broke up with Styles on Jan. 4, reportedly following a dispute they had while on vacation on the Virgin Islands. The source added that Swift held on to a necklace Styles made for her and added it to a "memory box" where she keeps mementoes from all her ex-boyfriends, which she then goes through for inspiration when writing new music. 

"Her main source of material for the songs she's written about her string of other famous ex-boyfriends comes from rooting around in a trunk where she hoards keepsakes of their relationships," the source said. "Photos of Harry are now in there, along with a chain he had made for her when they got together last year which matches his own favourite necklace, of a paper plane."

The trinkets provide "easy material" for Swift to write a song out of, the source added. 

Swift was spotted heading into a recording studio on Jan. 10, only days after splitting from Styles, and that same day she tweeted, "Back in the studio. Uh oh..."

"Taylor writes music in the same way that other women chat to their friends on the phone. It's been how she deals with her emotions for most of her life," an insider said. 

Swift admitted in the past about the fact that she draws inspiration for her music from her personal relationships. She told Us Weekly in 2010, "I've always lived by the theory that if a guy doesn't want me to write a bad song about him, he won't do bad things. And he shouldn't, you know?"