Aesop's Fables or Aesopica refers to a collection of fables credited to Aesop, a slave and story-teller who lived in ancient Greece between 620 and 560 BC. Aesop's Fables have become a blanket term for collections of brief fables, especially beast fables involving anthropomorphic animals. His fables are some of the most well known in the world. The fables remain a popular choice for moral education of children today. Many stories included in Aesop's Fables, such as The Fox and the Grapes (from which the idiom "sour grapes" was derived), The Tortoise and the Hare, The North Wind and the Sun, The Boy Who Cried Wolf and The Ant and the Grasshopper are well-known throughout the world.