This is the second track from Vulnicura, an album that details the breakdown of Björk's relationship with artist Matthew Barney. This song finds her singing about wanting to find clarity: "Moments of clarity are so rare. I better document this."

During an interview with Pitchfork, Björk was asked if writing a song about something that has happened bring her clarity on the other end? She replied: "Yeah, I think so. When it works. I go for a lot of walks and I sing. That's when you find an angle on things, where it makes sense for that particular moment. It's more that feeling. In a way, I also rediscovered music, because [crying] - I'm sorry - it's so miraculous what it can do to you; when you are in a really f--ked situation, it's the only thing that can save you. Nothing else will. And it does, it really does. I'm hoping the album will document the journey through. It is liberation in the end. It comes out as a healing process, because that's how I experienced it myself."

Venezuelan producer Alejandro Ghersi, (aka Arca) produced six of Vulnicura's nine tracks. Björk approached Arca after his manager sent her Arca's mixtape &&&&&. She told Pitchfork: "Alejandro knew all of my albums from his childhood - apparently, I'm big in Venezuela. [laughs] He knew my songs better than me. I would say, 'Oh, can you make that third beat like…' And he'd say, 'Oh, you mean like the third break of song five of album two?' He was like a library of my music."

"At first, I was really defensive; I'm not good with people who are fans," Bjork continued. "But it just wasn't that energy at all. It was a really healthy energy, like a student. Suddenly, I got to be a strange kind of teacher. I would literally sit next to him and, for the first few songs, the heartbreak songs, I would be the backseat driver. I would describe all the beats, and then he would do them and add stuff. We did it together. I've never done that before. So I just sat next to him for weeks, and we did the whole album. It's the quickest I've ever worked. He's so incredibly talented and so eager to learn."

"It's one of those crazy things in life where people from opposite ends meet, and you've got so much to teach each other," she added. "It's really equal, what you've got to give to each other. [tears up] It's been a strange album - the most painful one I've done, but also the most magic one."

The video was directed by the Dutch fashion photographer duo Inez & Vinoodh. It finds Björk dressed in the same celestial garb as featured on the Vulnicura album cover with viewers able to see her heart visibly beating through her chest.

Inez & Vinoodh are well known for their video and photographic work in the high fashion world. They collaborated with Lady Gaga on her ARTPOP project including the "Applause" single and also directed Rihanna's "FourFiveSeconds" clip. The Dutch pair have also worked extensively with Bjork in the past, including on her 2011 Biophilia set. Their collaboration with the Icelandic singer in 2001 on her "Hidden Place" video, features a similar performance to this visual.

This reflection on the polarising numbness before a relationship collapses was written by Björk about her time with Barney before the implosion of their partnership. For three weeks, the Icelandic singer had been unable to speak following surgery for a knot in her vocal chords. When she healed, something clicked: "I was in this forest outside Reykjavik, warming up, opening my throat like a bird," she told Rolling Stone. "It was cathartic– you realize the tension that built up, because you are protecting that part of you." This song came out of the experience.