Born in Netherland in 1910. After living in Italy, he emigrated to the United States and worked as an illustrator and graphic designer. And then he returned to Italy again, where he died in 1999. After publishing his first picture book, Light Blue and Light Yellow, in 1959, he won the Caldecott Award for four other works, including Swimmy, Frederick, and Alexander and the Wind-up Mouse. In Japan, it is published in Japanese elementary school textbooks and is widely popular.