James and Lorde were together for around three years before their split.
"G2g brb just gonna make up an interpretive dance to this magnificent bop for the ages", Swift wrote.
Some of her more mysterious "Green Light" musings?
Teaming up with Jack Antonoff, Lorde had a hand in co-producing every song.
New Zealand singer Lorde was influenced by the late David Bowie while writing her new music.
Lorde's upcoming album, "Melodrama," is set to release this summer.
It has been a minute since we last heard from Lorde, but today that all changes. It was my first major heartbreak.
"I moved out of home and into my own house and basically just had this awesome year of independence and freedom and figuring out all this stuff about myself".
"I moved out of home and all of a sudden I was kind of figuring out, who am I when I'm alone?"
"Green Light" is also varied, changing in the same way a person changes after a meaningful relationship draws to a close and moving away from brooding ("She thinks you love the beach, you're such a damn liar") to something more positive ("I'm waiting for it, that green light, euphoric!").
That journey of self-discovery is what also led the "Tennis Court", singer to find a completely new sound for this record. "It had to be really special and really singular and it couldn't sound the same as the old stuff and there was a lot of discovery that went on".
"We have a ton of awesome leftover songs that just didn't quite fit inside the world of Melodrama", Lorde tweeted. Let us know what you think of the song and what Lorde had to say in the comments section below.
And in a tweet posted shortly after Green Light's release, Little said he was "really proud" to be part of the song's creation.