At age 10, Marsai Martin made her first pitch as a future executive: she proposed the idea that would become the movie Little, a riff on the 1988 Tom Hanks hit Big, released earlier this year. Martin, now 15, also starred in the movie and became one of its executive producers, the youngest person ever to hold that title for a major-studio release—and all of that on top of her regular gig as a star of ABC’s Black-ish. Now Martin heads her own production company, Genius Productions; its first release, a comedy called StepMonster, is already in the works. Her aim is to tell more stories, with diverse casts, that people her age can relate to—in other words, she’s shaping the culture, a far cry from just selling it to an audience. —Stephanie Zacharek