These women sent a generation of astronauts into space. Now Hollywood is telling their story.

Although mathematician Katherine Johnson was honored last year with the Presidential Medal of Freedom, few know just how integral she was to the U.S. space race.

Fortunately, many more soon will. Her story is being made into the movie “Hidden Figures,” which tells the tale of how Johnson and several other black women played a pivotal role in helping the U.S. send men into space and bring them back safely.

Johnson, who worked at NASA and its predecessor agency from 1953 until 1986, was responsible for calculating flight plans for astronauts from Alan Shepard and the Mercury Project through the Space Shuttle. In the process, she broke down all manner of barriers and stereotypes about the role black women in particular could play in math and science.

The film, set to hit theaters in January, brings Johnson’s story to life with Taraji Henson playing Johnson, along with a cast that includes Octavia Spencer, Janelle Monáe, Kevin Costner, Kirsten Dunst and Jim Parsons.

A new trailer, posted to YouTube this past week, offers a peek at what to expect from the film:

But even better is to hear Johnson, who turns 98 this week, tell how she calculated the flight path to take astronauts to the moon and back. She recalled her work in a short film for Makers.com.

Johnson recalls doing the early math by hand and then holding her breath that the numbers were right and that the astronauts stuck exactly to that flight path.

When the work was later handed over to computers for a 1962 mission, John Glenn insisted Johnson recalculate the math.

“The computer is right,” she told Glenn. “It took me a day and a half to compute what the computer had given him. Turned out to be the exact numbers they had.”

This article originally appeared on Recode.net.