Scarlett Johansson is one of the sexiest stars in Hollywood, placing 15th on Maxim's 2013 Hot 100 list.


But her co-star and friend Joseph Gordon-Levitt says her sex appeal comes from a lot more than just her looks. Gordon-Levitt cast Johansson in his directorial debut, "Don Jon," which he also wrote and stars in.


But why did he cast her?


"I didn't know Scarlett, but I spent more than a year with the image of her in my head playing this character. She couldn't not do this," the actor tells Men's Health in the magazine's October issue.


"Look, Scarlett is a gorgeous, gorgeous woman, but if you just compare purely physical features, plenty of girls are just as gorgeous," he continues. "But she creates this extra something. It's in her walk, her eye contact. The total package is just off the charts."


We're sure Johansson's fiance Romain Dauriac, who just popped the question with a stunning art deco diamond ring, feels the same way Gordon-Levitt does.


See JGL's Men's Health cover below:


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  • NEW YORK, NY - JANUARY 17: Actress Scarlett Johansson attends the curtain call for the 'Cat On A Hot Tin Roof' opening night at Richard Rodgers Theatre on January 17, 2013 in New York City. (Photo by Stephen Lovekin/Getty Images)




  • NEW YORK, NY - JANUARY 17: Actress Scarlett Johansson attends the 'Cat On A Hot Tin Roof' Broadway opening night after party at The Lighthouse at Chelsea Piers on January 17, 2013 in New York City. (Photo by Stephen Lovekin/Getty Images)




  • NEW YORK, NY - NOVEMBER 27: Scarlett Johansson attends 'Cat On A Hot Tin Roof' photo call at Sardi's on November 27, 2012 in New York City. (Photo by Ben Gabbe/Getty Images)




  • NEW YORK, NY - NOVEMBER 18: Actress Scarlett Johansson attends the 'Hitchcock' New York Premiere at Ziegfeld Theater on November 18, 2012 in New York City. (Photo by Neilson Barnard/Getty Images)




  • CHARLOTTE, NC - SEPTEMBER 06: Actress Scarlett Johansson speaks on stage during the final day of the Democratic National Convention at Time Warner Cable Arena on September 6, 2012 in Charlotte, North Carolina. The DNC, which concludes today, nominated U.S. President Barack Obama as the Democratic presidential candidate. (Photo by Chip Somodevilla/Getty Images)




  • NEW YORK, NY - MAY 07: Scarlett Johansson attends the 'Schiaparelli And Prada: Impossible Conversations' Costume Institute Gala at the Metropolitan Museum of Art on May 7, 2012 in New York City. (Photo by Dimitrios Kambouris/Getty Images)




  • HOLLYWOOD, CA - MAY 02: Actress Scarlett Johansson and actor Jeremy Renner pose as Scarlett Johansson is honored with a star on The Hollywood Walk Of Fame on May 2, 2012 in Hollywood, California. (Photo by Jason Merritt/Getty Images)




  • HOLLYWOOD, CA - MAY 02: Actress Scarlett Johansson is honored with a star on The Hollywood Walk Of Fame on May 2, 2012 in Hollywood, California. (Photo by Jason Merritt/Getty Images)




  • ROME, ITALY - APRIL 21: (L to R) Actors Tom Hiddlestone, Scarlett Johansson and Mark Ruffalo attend 'The Avengers' photocall at De Russie Hotel on April 21, 2012 in Rome, Italy. (Photo by Elisabetta Villa/Getty Images)




  • LONDON, ENGLAND - APRIL 19: Scarlett Johansson attends Marvel Avengers Assemble European Premiere at Vue Westfield on April 19, 2012 in London, England. on April 19, 2012 in London, England. (Photo by Gareth Cattermole/Getty Images)




  • US actress Scarlett Johansson arrives for the Dolce & Gabbana Spring-Summer 2012 ready-to-wear collection on September 25, 2011 during the Milan's women fashion week. AFP PHOTO / FILIPPO MONTEFORTE (Photo credit should read FILIPPO MONTEFORTE/AFP/Getty Images)




  • CULVER CITY, CA - JUNE 04: Actress Scarlett Johansson arrives at Spike TV's 5th annual 2011 'Guys Choice' Awards at Sony Pictures Studios on June 4, 2011 in Culver City, California. (Photo by Frazer Harrison/Getty Images)




  • CULVER CITY, CA - JUNE 04: Actress Scarlett Johansson arrives at Spike TV's 5th annual 2011 'Guys Choice' Awards at Sony Pictures Studios on June 4, 2011 in Culver City, California. (Photo by Jason Merritt/Getty Images)




  • SANTA MONICA, CA - APRIL 20: Actress Scarlett Johansson arrives at an Evening of Cocktails and Shopping to Benefit the Children's Defense Fund hosted by Coach at Bad Robot on April 20, 2011 in Santa Monica, California. (Photo by John Shearer/Getty Images for Coach)




  • WASHINGTON, DC - APRIL 30: Scarlett Johansson attends the 2011 White House Correspondents' Association Dinner at the Washington Hilton on April 30, 2011 in Washington, DC. (Photo by Kris Connor/Getty Images)




  • LOS ANGELES, CA - FEBRUARY 27: Actress Scarlett Johansson arrives at the 83rd Annual Academy Awards held at the Kodak Theatre on February 27, 2011 in Hollywood, California. (Photo by John Shearer/Getty Images)




  • WEST HOLLYWOOD, CA - FEBRUARY 27: Actress Scarlett Johansson arrives at the Vanity Fair Oscar party hosted by Graydon Carter held at Sunset Tower on February 27, 2011 in West Hollywood, California. (Photo by Pascal Le Segretain/Getty Images)




  • HOLLYWOOD, CA - FEBRUARY 23: Actress Scarlett Johansson attends Vanity Fair Campaign Hollywood 2011 continues with the Cosmopolitan of Las Vegas & The Art of Elysium 'Pieces of Heaven Art Auction' held at Siren Studios on February 23, 2011 in Hollywood, California. (Photo by Charley Gallay/Getty Images for Vanity Fair)




  • Actress Scarlett Johansson arrives on the red carpet for the 68th annual Golden Globe awards at the Beverly Hilton Hotel in Beverly Hills, California January 16, 2011. AFP PHOTO / Robyn Beck (Photo credit should read ROBYN BECK/AFP/Getty Images)




  • Actress Scarlett Johansson arrives on the red carpet of the 68th annual Golden Globe awards at the Beverly Hilton Hotel in Beverly Hills, California, on January 16, 2011. AFP PHOTO/Valerie MACON (Photo credit should read VALERIE MACON/AFP/Getty Images)




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