Born in Astoria, Queens in 1995, Martinez grew up on Long Island in a family of Dominican and Puerto Rican heritage. A self-described emotional child, she struggled to fully express herself in her family's traditional household and was drawn early on to poetry, art, and music. She taught herself how to play guitar, and by her teens was adept at play covers and writing her own songs. In 2012, while still in high school, she won a spot on NBC's The Voice with her performance of Britney Spears' "Toxic." Choosing to join judge Adam Levine's team, she eventually made it to week five before getting eliminated via audience vote. Martinez began working on solo material and in 2014 released the Kinetics- and One Love-produced EP Dollhouse on Atlantic Records.
In 2015, she returned with her debut full-length album, Cry Baby, which featured the singles "Pity Party" and "Sippy Cup." The record reached number six on the Billboard 200 and hit number one on Billboard's Top Alternative Albums chart. After the release, Martinez quickly started working on the follow-up, but after numerous delays the album wouldn't be finished until 2018. That same year, she also recorded a full-length movie to accompany the release. The album K-12 was issued in September 2019 and continued the adventures of Cry Baby, the character who had dominated Martinez's debut LP. 2020 brought the dreamy harp-led single, "Fire Drill," along with the buoyant "Play Date." ~ Matt Collar, Rovi