The Fords, who live in Washington, D.C., sought guidance from gender experts and mental health practitioners. Ellie, they said, was “consistent, insistent, and persistent” in her gender identity, which experts say is a hallmark for those who are transgender — those whose gender identity does not align with the gender they were assigned at birth. An estimated 1.4 million adults in the United States currently identify themselves as transgender.

Though many children will experiment and play with a range of gender roles at different points in their life, early data reveals that kids who truly are resolute about their gender identity are unlikely to feel differently as adults.

The Fords felt certain that their child was not merely going through a phase. In fact, the Fords said, once she began to express herself and dress as she wished she immediately blossomed into a happier child. She chose the name Ellie, inspired by a favorite stuffed elephant.

The Fords said they went public with their story because they feel it is important to raise awareness about transgender issues and to humanize and normalize gender nonconforming people.

The editors at National Geographic said they had similar motivations for devoting their magazine issue and documentary to the subject. National conversations surrounding transgender rights (such as the battles over restroom laws) and gender equity (including the quest for equal pay for women and parental leave for fathers) call for examination, said Susan Goldberg, editorial director of National Geographic Partners and the first female editor in chief of the magazine. “Families are grappling with these issues, schools are, the courts are, and legislators at all levels of government are — and science is looking more at it too,” Ms. Goldberg said.

Even the language we use to talk about gender has changed. Facebook offers more than 50 gender options. National Geographic developed a glossary of terms and a discussion guide for parents, teachers and children.

“We’re in the middle of a real historical, cultural shift,” said Christia Spears Brown, a professor of developmental psychology at the University of Kentucky and author of “Parenting Beyond Pink and Blue: How to Raise Your Kids Free of Gender Stereotypes.” “The complexity of gender has always been there, we’ve just long ignored that it’s much more complex than we want it to be.”