Mila Kunis Spills All the Juicy Details on How She and Ashton Kutcher Got Together: We Started Out as Friends

This video is unavailable because we were unable to load a message from our sponsors.

If you are using ad-blocking software, please disable it and reload the page.

The road to romance for Mila Kunis and Ashton Kutcher is certainly an interesting one.

Kunis appeared on Howard Stern's SiriusXM show on Tuesday, and the notoriously private actress surprisingly went into plenty of detail about how she and husband Ashton Kutcher's relationship turned romantic. The two had been friends since their days starring on That '70s Show, but Kunis dished that when she ran into him again in 2012, they both decided to try to be "friends with benefits."

"We, oddly, both did a movie called -- I did Friends With Benefits, he did a movie called No Strings Attached," Kunis, 32, says. "If we just paid attention to these movies, we should know that sh** like this does not work out in real life. Well, we clearly didn't pay attention. We shook hands, we're like, 'Let's just have fun!' I mean, literally we lived out our movies. We literally just had a very open conversation."

WATCH: Mila Kunis Dishes on Marriage to Ashton Kutcher, Reveals What She's Learned From Being a Mom -- 'Children Are F**king Crazy'

Kunis says Kutcher's good looks "took [her] breath away" when she ran into him again at an awards show after having not seen him in a while, and that their rekindled relationship started when he invited her over for a housewarming party. Kunis brought a girlfriend with her, but admits that she suddenly got "butterflies" in her stomach. Although Kutcher, 38, originally wanted to set up Kunis with a friend of his at the party, he later became "territorial."

Of course, one thing led to another.

"So, I went over, long story short -- I didn't leave 'till the next morning," Kunis says. "And that was the first time, ever, that I'd ever slept over when I was single... at a guy's house."

"Well, I'll tell you this much, he didn't let me leave," she adds. "At two in the morning I was like, 'I'm gonna call an Uber! See you later.' And he was like, 'You're crazy!' And I was like, 'Bye! (laughs)' Like, when I was single, I was so adamant about never, as stupid as it sounds, never staying over at a guy's house. I was, like, peacing out, and he was like, ‘You're not leaving.’ And that was the first time and only time."

Still, the two both had plenty of reservations, given that Kutcher had been single for only eight months since splitting from his ex-wife, Demi Moore, in 2011. Kunis was also "having the best time" being single after splitting with Macaulay Culkin that same year, after nine years together.

"I thought he was going to go on a mad tear after he broke up with Demi," Stern bluntly comments about Kutcher, to which Kunis agrees, "You and I both, Howard! So, then we end up having a lot of talks about how this is a huge mistake, and how he needs to be single and I need to go and be single."

"We both were in agreement. 'Yeah, this is just fun. Just fun.' Shook hands on it. Just fun," the actress recalls. "Three months later ... I was like, 'This isn't fun anymore! (laughs)'"

But Kunis insists that the two were still completely honest with one another -- even about their other hookups.

"We were always very open with one another," Kunis says. "Whoever was in our so-called stable, or whatever you want to call it. I was like, 'I'm gonna go see my friend.' And he was like, 'ughh...'"

Eventually, they both figured out they wanted to be exclusive.

"We'd literally attempt to go see other people, and then that night we'd be like, 'Hey! What are you up to? Wanna come over?'" she recalls. "It ended up going from just having fun to genuinely wanting... When I realized I was nervous was when I spoke to him. I was like, 'I don't like this anymore.'"

These days, the two couldn't look more enamored with one another. The couple tied the knot last July and have one daughter together, 1-year-old Wyatt. The Bad Moms star is currently pregnant with their second child.

WATCH: Mila Kunis Goes Makeup-Free and Flaunts Her Baby Bump

Earlier this month, Kunis opened up about her marriage to Glamour.

"There's nothing we don't know about each other because we've known each other for so long: the ugly, the bad, the good," Kunis said. "We went through a period where I thought he was crazy. At the height of his career, I was like, 'Ugh, I don’t like you. I don’t even know you anymore,'… then we’d get back together and be like, 'Oh, sorry. I didn't mean to overreact.'"

"It truly is being married to your best friend. That’s a cliché; it's cheesy. But it's true," she added.

Watch below: