Released in 2001 on Hilary Duff's self-titled debut album, "Who's That Girl" serves as a defining track from the early teen pop era. The song showcases Duff's signature vocal style, blending youthful energy with a polished production typical of mid-2000s pop music. As a lead single, it helped establish her career and resonated with a generation of young listeners seeking relatable themes of friendship and self-discovery. The recording reflects the commercial sound of the time, featuring catchy melodies and upbeat rhythms that became staples of radio play during her rise to fame. This track remains a significant part of her discography, representing the transition from child star to a dedicated pop artist.