Google have redesigned their famous logo in tribute to the children's book The Very Hungry Caterpillar.
The book, which is forty years old today, was written and illustrated by Eric Carle - a graphic designer who later became art director of an advertising agency before moving into book illustration full-time.
The original idea for The Very Hungry Caterpillar came to Carle while he was working in his studio.
"One day I was punching holes with a hole puncher into a stack of paper and I thought of a bookworm" Carle told The Times' education supplement.
"And so I created a story called 'A Week with Willi the Worm'. Then my editor suggested a caterpillar instead and I said 'Butterfly!' That's how it began."
Carle, who turns 80 this year, still receives some 10,000 letters a year from children who read the book. The Very Hungry Caterpillar has sold more than 29 million copies around the world and has been translated into 47 languages. It still sells on average one copy every 30 seconds.
The search engine Google has a history of posting special-theme Google logos. Last month it posted a Dr. Seuss birthday logo.