Director Mike Mills on the real people who inspired '20th Century Women'

"It's all about the mother," says Julie (Elle Fanning) to Dorothea (Annette Bening) in 20th Century Women. That's the secret employed by the film's writer and director Mike Mills, as discussed in a new featurette debuting exclusively by Mashable.

"Dorothea...is based a lot on my mom," Mills says in the video. In fact, the characters in Mills' film are all based on elements of women he knows, who he observed and interviewed as part of the writing process.

"The way I write, I don't really create characters; I kind of find existing, real people and work off of them," Mills says.

Hopeful Oscar contender 20th Century Women stars Bening, Fanning and Greta Gerwig as Abbie -- three generations of women who all influence Dorothea's son Jamie (Lucas Jade Zumann).

"Abbie is based on people who are really close to me, and all the stuff that happened in her life happened to some women I know," Mills elaborates. "And the same with Julie; Julie is a lot of girls I had crushes on in junior high and high school."

Mills pulled together disparate elements of the women he knows to make the characters in 20th Century Women feel real -- universal in their specificity.

20th Century Women releases on Christmas Day.