Recursion

A child couldn't sleep, so her mother told her a story about a little frog,
    who couldn't sleep, so the frog's mother told her a story about a little bear,
        who couldn't sleep, so the bear's mother told her a story about a little weasel...
            who fell asleep.
        ...and the little bear fell asleep;
    ...and the little frog fell asleep;
...and the child fell asleep.

See also: Self-reference.