"The Lorax," 1971

Famed children's author Dr. Seuss, who held a PhD in library science, used playful prose, catchy phrases and rhymes to tell important stories. While some questioned it, Seuss believed children had as much potential to solve apparently insurmountable challenges -- like environmental degradation -- as adults. This is evident in The Lorax, when a boy holds the last seed of the extinct "Truffula tree."