"Horton Hears A Who!" is a children's book written by Dr. Seuss. The story follows an elephant named Horton who discovers a tiny world called Whoville on a speck of dust. Horton learns that the inhabitants, known as Whos, are in danger and vows to protect them, despite being ridiculed by other animals. The central theme of the book emphasizes the importance of kindness and the idea that "a person's a person, no matter how small." Through his adventures, Horton teaches readers about compassion, responsibility, and the significance of every individual, no matter their size.