Emma Stone knows "everything" she needs to about her 'La La Land' co-star Ryan Gosling after they had ballroom dance lessons.

Emma Stone

Emma Stone

The 37-year-old actress had a "great" time working with the 35-year-old hunk - who she previously starred with in 'Crazy Stupid Love' and 'Gangster Squad' - on the musical romance, and though they were already good friends, she was blown away by his moves on the dancefloor.

She said: "To work with Ryan again, who is my buddy, it's wonderful to get to work with someone you know and trust so much as an actor and as a human being. So it was great.

"I knew he could sing and dance, but we had to learn to ballroom dance together.

"Once you've learned to ballroom dance with somebody, I mean, you've learned everything you need to know. If you want to get to know someone, take some ballroom dancing classes with them. He's very good at leading."

Emma plays barista and aspiring actress Mia opposite stubborn wannabe jazz pianist Ryan in the movie, and the actress hopes young people will put aside their cynicism and be encouraged to follow their dreams.

Speaking at a press conference for the film, she said: "When Conan O'Brien left his show [in 2010]... he made a speech at the end of it, and he said 'to let go of cynicism' and that 'cynicism was the ugliest quality' to him.

"And I think something about Damien [Chazelle, director] and what Damien created, and the hopefulness and the joy and the beauty of this medium but also this story... this movie is in no way cynical.

"It's about dreaming, and hoping, and working toward something to achieve something, and I think young people have fallen into a lot of cynicism, and making fun of things, and pointing out the flaws in everything, and this movie is anything but that. So it's a huge joy to be a part of it and show it to young people. This is what I hope young people will do - work hard to achieve their dreams and hope, instead of be cynical."