Hilary Duff first made a name for herself on the enormously successful Disney Channel/ABC Kids show Lizzie McGuire, which she parlayed into dual careers as a pop singer and film actress. Like most overnight successes, however, she paid her dues for several years before her big break. Appearances in the 1997 western True Women, 1998's Casper (as the Friendly Ghost's human friend Wendy), and 1999's The Soul Collector paved the way for her best-known role. Lizzie McGuire, which chronicled the ups and downs of a junior high schooler's life using live-action and animated clips, debuted in 2001 and quickly became a hit with the preteen set. Aside from the show's unique format, one of the main reasons for its success was Duff herself. As Lizzie, she was pretty, funny, and smart, but not intimidatingly so; she had two best friends, Gordo and Miranda, so she wasn't super-popular or an outcast; and she was confident enough to blaze her own trail, but still vulnerable enough to have crushes on unattainable boys.

At the same time Lizzie was taking off, Duff also appeared in the indie film Human Nature, reflecting her continuing big-screen aspirations. Lizzie McGuire mania continued through 2002, and Duff began her first steps toward her singing career with the song "Santa Claus Lane," which appeared on the soundtrack to The Santa Clause 2, as well as her own Christmas album, also named Santa Claus Lane. That year, production ended on Lizzie McGuire, freeing up Duff to pursue other opportunities. Episodes of the show continued to run into 2003, but by that time Duff had begun to move on, appearing in the teen spy movie Agent Cody Banks and playing Lizzie one last time in The Lizzie McGuire Movie, where funnily enough, she goes to Italy and is mistaken for a teen pop star. The soundtrack to the movie also featured several songs by Duff, including the singles "Why Not" and "I Can't Wait," which were both successes in their own right. The soundtrack went platinum in summer 2003.

Around that time, Metamorphosis, Duff's bona fide debut as a singer, was released. The album had a hipper and more eclectic sound than any of the material she had been given previously, and helped establish her as a personality outside of her Lizzie McGuire fame. The album charted at number two on the Billboard 200 on the week of its release, and its single "So Yesterday" topped the pop singles chart earlier that summer. Duff's omnipresence in 2003 continued with appearances at that year's MTV Video Music Awards and the Nickelodeon Kids Choice Awards, where she accepted Lizzie McGuire's trophy for Favorite TV Show. She also appeared in that year's film Cheaper by the Dozen and embarked on a tour that fall.

Duff remained just as busy in 2004. She appeared in movies like A Cinderella Story, Agent Cody Banks, and Raise Your Voice, and also released her self-titled second album, which exchanged the neutral fluffiness of Metamorphosis for an anthemic rock-pop style consistent with efforts from Ashlee Simpson and Avril Lavigne. The record continued to shape Duff's public persona, which was a continually evolving dynamo of branding, image, and teenage ambition. Released on September 28th (her 17th birthday), Hilary Duff eventually peaked at number two on both the Billboard 200 and the Top Internet Albums charts, and helped Hilary net "Most Searched by Kids and Teens on AOL" honors and more Nickelodeon Kids Choice Awards. Publicity for the album continued into 2005. That June, The Perfect Man debuted; in a bit of genius casting, it featured Heather Locklear as Duff's unlucky-in-love mother.

In July, Duff started preparing for the August release of Most Wanted. The collection included three new songs -- including the single "Wake Up," written by Benji and Joel Madden from Good Charlotte -- as well as remixed versions of past Hilary hits like "So Yesterday" and "Come Clean." There was also the Most Wanted tour, which stretched into September, ending just in time for her 18th birthday. By this point, the Hilary Duff promotion machine was in overdrive: her website offered a pay-as-you-go mobile phone branded with her name and bundled with Hilary-themed ringtones and wallpapers. During 2006, Duff worked on the films War Inc. and Material Girls, and also found time to work on her fourth album, Dignity, which was inspired in part by her breakup with Joel Madden. Dignity was released in spring 2007, inspiring favorable reviews from critics but relatively lukewarm sales from the public; nevertheless, it was certified gold from the RIAA.

Following Dignity, Duff stayed away from music for a prolonged period of time. A hits album called Best of Hilary Duff appeared in time for Christmas 2008. During this time, she continued to act -- notably, she appeared in the Polish Brothers' 2011 film Stay Cool -- and she also launched a young adult novel series called Elixir in 2010; the three books in the series were co-written with Elise Allen. Duff began working on her next album in 2014, completing the record in 2015. Preceded by the single "Sparks," Breathe In. Breathe Out. saw a June release; it debuted at five on the Billboard charts.