Julia Roberts believes "kissing" is the secret behind her successful marriage with Danny Moder.

Asked what advice she'd give other couples, she told host Mario Lopez on 'Extra': "I don't know. Probably kissing, right?"

The couple, who have twins Hazel and Finn, 11, and son Henry, eight, recently worked on the movie 'The Secret in Their Eyes' together but, despite spending all day together, they have admitted they had no problem differentiating their career from personal life once the working day was done.

Julia explained: "We did all that [work] in the day and in the car, and by the time we got home, we were able to just put it all away, which was really delightful."

Meanwhile, the brunette beauty, who married the cinematographer in 2002, recently praised Danny for making her "genuinely happy" and believes a lot of her success is down to him and his skills.

She said: "I don't know if I would have succeeded in some of the efforts that I made if he hadn't been in such close physical proximity to me. There's something about having the safest place in the world for you in the same room."