The Very Hungry Caterpillar (1969) is the most famous book by American children's author Eric Carle.  It is one of the best-selling picture books of all time, with sales of more than 30 million.

It's about a caterpillar who wakes up on Sunday morning and whose appetite increases through the week.  By Saturday night he is at least as big around as he is tall; then he hibernates in his cocoon and becomes a butterfly the next Sunday morning.