"First Man" screenwriter Josh Singer is known for making "based on true story" movies — "Spotlight," "The Post" — that really do recount what happened, without too many Hollywood embellishments.

Singer told Business Insider what the challenges were of giving Neil Armstrong's story the same treatment.

When Hollywood needs a true story to be told on the big screen, it often turns to one guy to write the script: Josh Singer.

And we don't mean a movie "based on a true story." We mean a real true story. And there is a difference.

For as long as there have been movies, the term "true story" has been used very loosely in Hollywood. To help move forward a plot or build more drama in a story, directors and screenwriters often embellish real events, or include moments that never happened.

Jim Garrison's memorable closing remarks in the trial scene in Oliver Stone's "JFK"? Never happened. Iranians chasing a plane down the runway at the end of "Argo"? Never happened.

It's extremely hard to not heighten true-life stories a tad because, let's face it, we want movies to be more exciting than real life. But Singer has found a way to tell gripping true stories for the screen without adding in tons of untrue elements.

What's his secret? It all comes down to the story, and lots of research.

Starting with "Spotlight" in 2015 — which earned a best-picture Oscar, and got Singer an original screenplay Oscar with director-cowriter Tom McCarthy — Singer has given audiences a glimpse of some of the most historic events and fascinating people in American history, with an accuracy to the account that even dazzles the people who were actually there.

"Spotlight" set the stage, as the movie's look inside the investigative-journalist unit at The Boston Globe that uncovered child sex abuse by Boston's Roman Catholic priests has been viewed as a modern-day "All the President's Men." And that might have been why Singer was asked to write last year's "The Post" (along with Liz Hannah), which looked inside The Washington Post as it published The Pentagon Papers. Now, Singer takes us to the moon with "First Man" (opening in theaters on Friday).

The movie, which is director Damien Chazelle's follow-up to six-Oscar-winner "La La Land," gives an intimate look at the events that led to astronaut Neil Armstrong's becoming the first man to ever set foot on the moon thanks to the successful Apollo 11 flight.

Starring Ryan Gosling as Armstrong, Chazelle doesn't go the route of "The Right Stuff" or "Apollo 13" in making the thrills of space travel the main focus (though there definitely is that). Instead, the focus is Armstrong himself, and how the deaths of some close to him leading up to Apollo 11 — particularly his daughter Karen, who died at age 2 — was a major burden he carried throughout the historic flight.

The relationship between Neil Armstrong (Ryan Gosling) and his daughter is the glue of "First Man." Universal

"I was just knocked out by how much we don't know about Neil Armstrong," Singer told Business Insider. "The story of his daughter — I never knew that."

As Singer read through James R. Hansen's official biography of Armstrong, "First Man: The Life of Neil A. Armstrong," which the movie is based on, he couldn't get over how much loss Armstrong suffered in the years leading up to the Apollo 11 launch. Following Armstrong's daughter's death in 1962 (from pneumonia, which was caused by her weakened state from a malignant tumor in her brain stem), Armstrong lost two close friends in the span of a year. Astronaut Elliot See died in a plane crash in 1966, and Armstrong's neighbor Ed White died in the Apollo 1 fire. Then Armstrong almost died manning Gemini 8.

With that, Singer and Chazelle had found their story for "First Man." It would be the emotional journey of a man who set out to do extraordinary things, and how much he was already dealing with. Then the challenge came of telling that personal story from the point of view of someone who gives little emotion.

"With a guy like Neil, who is so internal, how do you get under that?" Singer said. "How do you get inside what that feels like? It was a real challenge."

Singer would not have to shoulder the entire challenge alone. Chazelle planned to give the movie powerful imagery of space travel to coincide with Armstrong's internal struggle, including incredible visuals of the moon landing shot on IMAX cameras. Then there's Gosling as Armstrong, who had already built a style of acting where he could give an emotional performance without saying much at all.

"First Man" screenwriter Josh Singer said he wanted to show just how hard it was to get to the Moon. Universal

But Singer was still tasked with building a script that would be the road map for everyone to follow. And he admitted that at a few points during writing he fell into the trap of embellishing real-life moments, and paid the price for doing so.

He recalled the scene when Armstrong gets a phone call about the Apollo 1 fire, which killed all the astronauts on board, including his good friend Ed White.

"Literally Damien and I talked about mimicking what was done in 'Goodfellas' where De Niro slams the phone handle on the receiver after getting word that Joe Pesci's character was killed," Singer said.

He wrote the scene with Armstrong showing De Niro-like emotion over the news of his friend's death. He then gave it to the author of the Armstrong biography, James Hansen, to read.

"He said, 'Neil would never have done that!'" Singer recalled. "So we wound up having this moment where you see Neil go dead in the eyes and you look down and he's literally broken the glass he was holding and he's bleeding. It's like you see how hard he's trying to contain himself in that moment. And with that Jim said, 'OK, maybe I could buy that.'"

Throughout the four years of researching and writing the script, Singer had to do a balancing act of making "First Man" a thrilling story but also true to those who knew Armstrong. He spent months with people involved at NASA at the time of the space race, former astronauts, and spoke with the Armstrong family.

Josh Singer. Eugene Gologursky/Getty

"I just felt a huge responsibility to get it right," he said.

But he and Chazelle also wanted to show just how hard it was to get to the moon.

"The myth is that these were superheroes that got there easily," Singer said. "The truth is this is actually very hard and they were ordinary men and women who sacrificed a ton to get there."

Singer said that was one of the big things that upset him most about the controversy around the movie about not having a scene wherein the American flag is planted on the Moon. That specific shot is not needed, Singer said, because the entire movie is a look at patriotic sacrifice.

"To be perfectly honest, I can understand why people who haven't seen the film are questioning why that isn't there, but if you see the film you understand why," he said. "The film is so deeply patriotic to begin with it's not necessary. We also don't have the call to Nixon. We're trying to get under the myth."

And those who know the history of American space travel and Armstrong's story believe "First Man" has done just that.

Singer recalled the reaction of one well-known space expert, Robert Pearlman, after seeing the movie.

"When he saw Neil crying after his daughter's death he said he realized he was going to have to totally rethink everything he knew about Neil Armstrong," Singer said.

Singer said the best feeling about doing these "based on a true story" scripts is that the attention to detail is so refined that even those close to the material get something out of it.

"To get to that level of detail and get it right, that to me is the ultimate," Singer said. "It can function as more than a movie, it becomes a contribution to how we think about something. Whether it's the Catholic Church or journalism or how we think about space."