Julia Roberts says constant 'kissing' is the secret to a long and happy marriage.

The 55-year-old Pretty Woman star believes the key to her more than two decades of marriage to 53-year-old cinematographer Daniel Moder is not forgetting to have a smooch.

The star also said they show each other affection as she appeared on the The Late Show with Stephen Colbert on Monday.

Pucker up: Julia Roberts said while on the Stephen Colbert show on Monday that constant 'kissing' is the secret to a long and happy marriage

The proof is in the picture: Stephen held up an image of the actress kissing her husband, Danny Moder

Roberts was plugging her series Gaslit when the topic turned to marriage.

After being asked by host Stephen Colbert - who has been married to his wife Evelyn McGee-Colbert for 28 years with whom he kids Madeline, 27, Peter, 22, and 20-year-old John - to reveal her tricks on the count to three.

The 55-year-old actress said immediately: 'Kissing'.

The 57-year-old talk show host said the key was taking the time to 'apologize' and immediately wanted to take it back.

The beginning: The stars hold each other during their wedding in 2002

She is sweet on her husband: The siren kisses Modern on the cheek in this Instagram photo

Happy family: Moder and Roberts with Kelly Slater and their kids Phinnaeus, Henry Daniel and Hazel in 2015 in Malibu

Stephen quipped: 'Well, I would like to apologize to my wife for not saying kissing.

Roberts and her spouse have a rare Hollywood love story that has lasted.

Julia wed Danny in 2002  after they met on the set of the Brad Pitt movie The Mexican in 2000.

He was working as a camera man on the film and she was the star. 

Go! After being asked by host Stephen Colbert - who has been married to his wife Evelyn McGee-Colbert for 28 years with whom he kids Madeline, 27, Peter, 22, and 20-year-old John - to reveal her tricks on the count to three. She said kissing

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It was love: Roberts and her spouse have a rare Hollywood love story that has lasted. Julia wed Danny in 2002 after they met on the set of the Brad Pitt movie The Mexican in 2000

She got her man on a movie set: He was working as a camera man on the film and she was the star

They went on to have three children:  17-year-old fraternal twins Hazel and Phinnaeus and 14-year old son Daniel.

The couple moved to San Francisco last year to have a more quiet life away from Southern California after living in Malibu for many years.

She said of Danny in 2003: 'He makes me feel my most comfortable self. I don't alter myself in any way.'

Julia has also been married to Lyle Lovett from 1993 until 1995, and was engaged to Kiefer Sutherland. 

She lives in the City By The Bay: The couple moved to San Francisco last year to have a more quiet life away from Southern California after living in Malibu for many years

On the show, Roberts wore a blue suit with red heart shaped buttons and an Ace card on her back. The looker added black stiletto heels.

She said she was 'nervous' to be on the show.

Elsewhere, Julia spoke about her new miniseries Gaslit. 

The Oscar winner couldn't help but gush over her co-star Sean Penn.

He plays her character Martha Mitchell's husband US Attorney General John N. Mitchell on the Starz show about the Watergate scandal, which was adapted from the Slow Burn podcast by journalist Leon Neyfakh.

Co-stars: Elsewhere, Julia spoke about her new miniseries Gaslit. The Oscar winner couldn't help but gush over her co-star Sean Penn. He plays her character Martha Mitchell's husband US Attorney General John N. Mitchell on the Starz show about the Watergate scandal, which was adapted from the Slow Burn podcast by journalist Leon Neyfakh. seen on Monday

She said: 'He doesn't want anyone to know how nice and sweet he is because it would destroy his reputation that he's worked so hard on. He had so much patience getting all of this makeup done.

'He just was rock steady. All his stuff on, he would just sit there.

Julia also enthused about working with George Clooney for the fifth time on their new rom-com Ticket To Paradise while 'heavily bubbled' due to the COVID-19 pandemic.

Julia said: 'We were heavily, heavily bubbled,' before saying of George that 'everything you think he is, he is more than that.'

GC fan: Julia also enthused about working with George Clooney for the fifth time on their new rom-com Ticket To Paradise while 'heavily bubbled' due to the COVID-19 pandemic. Julia said: 'We were heavily, heavily bubbled,' before saying of George that 'everything you think he is, he is more than that'