After playing an aspiring actress in 2016's "La La Land," Emma Stone will star next in the upcoming biographical film "Battle of the Sexes." In it, she plays Billie Jean King, a former World No. 1 professional tennis player.

While Stone has had the pleasure of playing Billie Jean King, it turns out the role was not all fun and games. In fact, she found the experience very challenging and overwhelming since it is her first time to play a real-life character.

"I've never played a real person before," Stone, 28, said in an interview with The Hollywood Reporter. "And it's, like, this person is an icon and an absolute bad--ss that I could never even hope to be exactly like... It was super challenging, but [King] was so warm and welcoming and open to all of it."

Stone has also undergone a huge transformation, gaining 15 pounds to effectively portray the role. She attributed her weight gain to high-intensity cardio training and a balanced diet high in fat, calories, and lean protein.

On top of that, "The Amazing Spider-Man" actress has thoroughly studied the way King spoke, including her gestures, body movements, and facial expressions. She also played tennis every day for three months and had one-on-one sessions with King.

"I was very much a novice," Stone said in one interview with The Daily Mail. "We played every day for three months, which was nothing compared to a lifetime for Billie Jean."

Following "Battles of the Sexes," Stone will star next as Abigail Masham in Yorgos Lanthimos' historical drama film "The Favourite." She has also been cast in Disney's live-action spin-off of "One Hundred and One Dalmatians."

In "One Hundred and One Dalmatians," Stone will play Cruella de Vil, a pampered London heiress who wants to steal the Dalmatians to use their fur for a coat. More details about the project will be announced soon.