Los Angeles, California - Billie Eilish has revealed how her self-image and mental state influenced some of her most famous hair transformations.

In an interview with the Los Angeles Times published on Tuesday, the 21-year-old opened up about her decisions to dye her hair several times throughout her career and dished on each era's significance.

"2019, that period of my life when I dyed my hair green, I was completely unstoppable," Billie said. "I felt like I was on the moon. And I remember at the time being like, I'm finally happy. I'd never been happy before, and I just wanted to stay happy."

After that came a more tumultuous period for the Grammy winner, and Billie admitted her jaw-dropping bleach-blonde dye job was an attempt to take back control.

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"At first, it was fun," she said. "I was really excited for the blonde era — like, Blonde Billie is gonna be so cool. But it did not go how I wanted it to go."

The Ocean Eyes singer explained that the makeover led her to struggle with her own sense of self, telling the outlet, "I completely had no idea who I was."

Eventually returning to black hair, Billie said that the journey helped inspire her chart-topping hit, What Was I Made For? from the Barbie movie.

The song's central idea of struggling with one's purpose, particularly in contrast to the expectations and desires of others, was drawn largely from Billie's own experiences.

Though she drew primary inspiration from Barbie's storyline, the Grammy winner shared that the track subconsciously pulled from her own life as well.

"I do this thing where I make stuff that I don't even know is… like I'm writing for myself, and I don't even know it," she told Zane Lowe in July.

What Was I Made For? has emerged as a breakout success from the soundtrack, earning Billie an impressive five nominations at the 2024 Grammy Awards.