1992: Leto made his acting debut as a shirtless hunk in an episode of a short-lived ABC sitcom called "Camp Wilder."
1993: Leto played another hunk, this time fully clothed, in another short-lived sitcom, "Almost Home."
1994: Leto jumped from television guest star to TV movie star when he played Alicia Silverstone's unhappily married husband in "The Cool and the Crazy."
1995: Leto began making a name for himself after playing Claire Danes' high school crush, Jordan Catalano, in short-lived, yet critically-acclaimed drama "My So-Called Life," which aired for just one season on ABC.
1995: Leto made the leap to the big screen with a small role in ensemble drama, "How to Make an American Quilt."
1996: Leto's first leading role on film was in small coming-of-age drama "The Last of the High Kings," which takes place in Dublin, Ireland during the summer of 1977.
1997: Leto and a finely-groomed mustache made a splash at the Sundance Film Festival when "Prefontaine," a biographical film about American long-distance runner Steve Prefontaine, premiered to praise. Unfortunately, the movie failed to make a dent at the box office.
1998: Leto put on period attire and put his British accent to the test when he led the cast of "Basil," a historical drama centering on a lonely, young aristocrat in turn-of the century England struggling to meet the approval of his overbearing father.
1998: Fans of the slasher horror genre should remember Leto playing an aspiring journalist who helps another college student discover who is behind the dramatic murders of their friends in "Urban Legend."
1999: Leto bleached his hair and put up his fists up for a small role in David Fincher's acclaimed drama "Fight Club." He became more unrecognizable once Edward Norton beat his pretty face to a bloody pulp.
1999: Leto continued to ditch his pretty-boy appearance when he covered his face in scruffy facial hair for a role in psychological drama "Girl, Interrupted," in which he played Winona Ryder's ex-boyfriend who was facing the Vietnam draft.
2000: Leto got axed by Christian Bale early on in "American Psycho," but his bloody death set to Huey Lewis and the News' "Hip to Be Square" is one of the most memorable in the cult film.
2000: Leto's promising future as an award-winning thespian was on full display in Darren Aronofsky's disturbing drama "Requiem for a Dream," in which Leto played a heroin addict. His performance should have successfully scared any viewers away from doing any drugs. Ever.
2002: Leto was recruited by "Fight Club" director David Fincher to corn-row his hair and star in "Panic Room" as one of three criminals after $3 million in bearer bonds hidden in the titular room where Jodie Foster and her young daughter are hiding.
2004: Leto played Greek historical figure Hephaistion opposite Colin Farrell as Alexander the Great in Oliver Stone's "Alexander."
2005: Leto played Nicolas Cage's morally conflicted younger brother and arms-dealing partner in Andrew Niccol's "Lord of War."
2005: Rock star Leto and his brother, Shannon, struck a pose at the 12th annual MTV Europe Music Awards where their band 30 Seconds to Mars performed after their second album, "A Beautiful Lie" was released earlier that year to chart-topping success.
2006: Leto chopped off his hair and grew out another 'stache to play Raymond Martinez Fernandez, one half of a murderous pair known as the "Lonely Hearts Killers," who lured their victims through personal ads.
2007: Leto was virtually unrecognizable after gaining 67 pounds to play John Lennon's killer, Mark David Chapman, in "Chapter 27." Despite Leto's commitment to being authentic to the psychotic character, the biographical drama was panned by most critics.
2009: After losing all of that "Chapter 27" weight, Leto put on "Bad Grandpa"-style prosthetics to look like a crazy old man in "Mr. Nobody."
2010: Leto rocked a pink mohawk while performing with his band at a music festival in Wales.
2011: Leto's hair defies gravity while posing with his bandmates outside of a screening of their music video for 30 Seconds to Mars song "Hurricane."
2012: Leto brought a burly beard to Germany for UNESCO Charity Gala in Dusseldorf.
2013: Leto rocked Las Vegas with 30 Seconds to Mars in September at the iHeartRadio Music Festival.
2013: After a four-year hiatus from acting, Leto lost 30 pounds to play an HIV-positive transgender character opposite Matthew McConaughey in "Dallas Buyers Club." His return to the screen was met with critical acclaim -- and an Oscar nomination.
2014: Leto won his first Golden Globe for "Dallas Buyers Club."
2014: Leto won his first Oscar for "Dallas Buyers Club."
2015: Leto goes pink to perform at iHeart Radio Music Festival in Las Vegas.
2015: Leto teases his scary look as the Joker in the 2016 DC Comics super-villain mash-up "Suicide Squad."