Octavia Spencer thought 'Hidden Figures' was "historical fiction" when she received the script.
The 46-year-old actress had no idea that black women played a significant role in the space race, and was convinced she would have heard the story before if it was true.
She said: "I thought it was historical fiction like 'The Help'.
"You know, your agents always send you a little teaser blurb: 'You'll be meeting with Donna Gigliotti about her upcoming project about three black female mathematicians who helped get our astronauts into space.' And I thought: 'OK, well, that's historical fiction, because I would know that story.' "
Octavia - who plays Dorothy Vaughan in the drama about three African-American women who were on the team that helped to launch astronaut John Glenn into orbit in the 1960s - is incredibly thankful NASA bosses overlooked race and gender and women of colour were able to be an "integral" part of the space race.
She told The Guardian newspaper: "You've got to remember they were all terrified of who was getting to space first.
"What would that mean, would they have missiles pointed at America? America had to get there, and they had to be competitive on that front. It behooved them to disregard gender. It behooved them to disregard race.
"Thank God they did... black and white women were integral to the space race."
And the 'Help' actress is thrilled Hollywood finally seems to be embracing diversity.
She said: "I love the small ones, I do. That's my thing, as an actor, when you find a small movie, and you know it's not going to get made unless some big names get attached to it.
"But the wonderful thing about it is the big tent-pole movies, if you look at it, like 'Captain America', they are getting more diverse in their casting. If you look at 'Star Wars', if you look at 'Thor'. That's important, because in that universe, you need to see people of colour, all people of colour, and now we are. That's the industry. That's the wonderful thing about the 'Divergent' series. You see all people, and that's where we need to continue to go."
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