Actress Julia Roberts says the secret to a successful marriage is kissing.

The 48-year-old spoke about her marriage of 13 years to cinematographer Danny Moder, 46, during an appearance on TV show `Extra`, reports dailymail.co.uk.

The `Eat Pray Love` star discussed her married life when she sat down with `Extra` host Mario Lopez to talk about her film `Secret In Their Eye`.

When Lopez asked relationship advice 'for other... entertainment couples' from the actress, Roberts made sure to clarity that her tip wasn't just for "entertainment couples".

She eventually shared a simple advice: `I don't know. Probably kissing, right?`

`Secret In Their Eyes` is a film about an investigator who's sudden case is her own daughter's death, featuring Roberts as the lead.