The seeds of the idea for Elemental came to Peter Sohn many years ago, in a middle school science class, looking at the periodic table.

"All I saw were apartment buildings," he says. "These blocks and the atomic number and the name to me was like a family or a person that lived there. I would come up with jokes like, 'Copper lives next to helium. But don't trust helium because they're gassy.'"

Coming up with jokes for boron and argon was trickier so, in the interest of storytelling possibilities, Sohn boiled the elements down to the classics: fire, water, earth and air.

Growing up in New York as the son of Korean immigrants, "There was a beautiful metaphor for me in this table of elements. There are all these disparate cultures mixing together."

Sohn is one of Pixar's MVPs. He joined the company in 2000, working in the art and story departments. His credits include WALL-E, Brave and The Incredibles. It was Sohn who helped design such memorable scenes as the dentist's office in Finding Nemo and the gazillion balloons lifting Carl's house over the city in Up.

"He can do everything," says Pete Docter, Pixar Animation Studio's chief creative officer and Elemental's executive producer. "He's a genius story guy, a brilliant designer. He's an amazing animator."

Sohn's Pixar colleagues have also recruited him to voice some of their characters including Emile in Ratatouille, Scott "Squishy" Squibbles in Monsters University and Sox in Lightyear.

In The Good Dinosaur, which Sohn also directed, he plays Forrest Woodbush (a.k.a. the Pet Collector). His physical appearance even inspired the character Russell in Up.

I recently met Peter Sohn in Chinatown where he and his family celebrated special occasions. I thought we'd be talking about the ins and outs of filmmaking. We did, but we also talked a lot about his parents.

"My mother's love for movies was this weird way that we could communicate because she didn't speak English very well," he remembers. "I spoke English better than I did Korean, and so much of growing up was this battle to try to understand each other. But when it came to the movies, there's this Venn diagram where we could connect."

New York City's different cultures inspired the metropolis in Elemental. Element City, as it's called in the movie, is "very much based off of these immigrant neighborhoods," including Little Italy and Koreatown, "I was so inspired by that," says Sohn.

Elemental was a chance to put his family's story on screen

Sohn's father emigrated to New York from Korea in 1969 with $150.

"$75 of that would go to rent in, I guess it would be like a prostitute apartment because, [when I was] a kid, he would just say, 'hooker house, hooker house.'" Sohn says he and his brother "had no idea" what their dad was talking about. "And then the other $75 would go to renting a hotdog cart," selling hotdogs, pretzels and icies in Manhattan.

Between the cart and other odd jobs, Sohn says his father saved enough money to buy a bodega-style grocery store in the Bronx.

"My mother was the cashier and my father kept working this four in the morning 'till 11:00 at night job, seven days a week." In Elemental, the father also works long hours.

When the shop did well, Sohn's family would go to Chinatown, especially the restaurant Hop Kee. "It was my parents' happy place," he recalls.

Inside the restaurant, Sohn recognizes the waiter. He tells him that his mother's favorite dish was the crab.

Sohn's memory is vivid. "The funny thing about my mom is that she's so loud eating the crab," he tells the server. Almost like he's voicing a character in a Pixar movie, Sohn mimics his mom smacking her lips together in delight. It's a "very exciting" dish, the server agrees.

Attention to detail and a wild imagination

Elemental is like a fantastical, kid-friendly, Romeo and Juliet. The Fire parents have emigrated to Element City where they open a grocery store. Their daughter, Ember, meets a Water character named Wade. She's a bit of a hothead. He's weepy.

Naturally, fire and water isn't a good mix but, through the magic of animation, they make it work. In one scene Ember shows off how she can turn the landscape different colors. Wade responds by making a rainbow.

Sohn says the idea is, "What would happen if they could get along?"

In the movie, Ember's Fire family hates the idea she's falling in love with Water.

Sohn says that tension mirrors his own experience.

"I fell in love with someone that wasn't Korean," he says, "I grew up in a family where they were like marry Korean. My grandmother's dying words were ... marry Korean ... there was a lot of pressure from that. But I fell in love with someone that wasn't."

Sohn gets a bit quiet when he says, "All the fun culture clash stuff from that and also the dark stuff from that became ingredients to the film."

When he was doing research for the movie, he asked his mom if they could walk around Chinatown together. She was being treated for pancreatic cancer.

"She wasn't doing great. She had been going through chemo," he says, "I remember her in her little knit cap that she was wearing." They went to Hop Kee — she had the crab — and strolled Chinatown's bustling streets. It was, Sohn says, "one of the last things I got to do with her."

Elemental took nearly seven years to make. During that time, both of Sohn's parents died. He says making this movie provided a degree of closure but, "There's still some open hole that I'm feeling that I don't know how to close up yet."

Heartache, family, falling love. Sohn says Elemental is about finding connection.

Audio and NPR.org versions of this story were edited by Rose Friedman and adapted to NPR.org by Beth Novey.