In this song, a little girl can't find her way until she becomes a woman and discovers a sense of self-worth. The track was co-written by Australian singer-songwriter Sia. "I love hearing a song that I feel like I could have written, in terms of the message," Clarkson told USA Today. "I feel powerful when I listen to that song."
Speaking on BBC Radio 1's Breakfast with Nick Grimshaw, Clarkson said of Sia. "I've never gotten to sing her songs before. She writes such rangy songs. We work with the same producers. So, we kind of have the same mutual friends."
Sia co-wrote the song with Jesse Shatkin, Steve Mostyn and Warren Felder. It was the last song Clarkson recorded for her Piece by Piece album. She told Nick Grimshaw: "They had just written it. They were like 'we think you could nail this.' And I was like, 'I think I could, too. I want it!'"
Kelly Clarkson was pregnant and super-hormonal when she recorded the song. She recalled to Billboard magazine: "I'm a huge fan of Sia in general, and my producer Jesse Shatkin and her had just written it, and he sent it to me and I got so excited. We got in the studio - he came to Nashville because I couldn't travel at that point - and we got to do these vocals, and what was great was that they let me do what I want."
"The vocal on the demo was already amazing, but they let me breathe with it for a minute," Clarkson continued. "I sat in the studio and said, 'I'm gonna try some things, they might sound horrible but I'm gonna try and go for some stuff.' I was just more of a vulnerable singer, and more willing to constantly try things."
Towards the end of 'Invincible,' it was like I went to church," she added. "I was having a good time singing that song. And I love that song - that message is so empowering, and that message is so raw."
The song finds Kelly Clarkson utilizing the very high end of her vocal range whilst Sia also supplies background vocals. "We have very different voices, so it rubbed really nicely," Clarkson noted to USA Today. "I kept hers, then I did all the same things and blended them together. I wanted it to sound like a swarm of vocals."