Guardians of the Galaxy director James Gunn was adamant: The movie wouldn't work, he said, if Groot didn't work. So explains Nicolas Aithadi, one of the geniuses behind Groot. Aithadi, now based in Vancouver, is nominated for an Academy Award along with three others on the Guardians team for visual effects. Marsha Lederman reports on the creation of the scene-stealing arboreal hero.