Eric Carle, the man who wrote and illustrated one of the most beloved children’s books of all time, and dozens more, died Sunday at the age of 91. His son said kidney failure was the cause of death.

Despite getting a late start on his chosen career path, Carle quickly made up for lost time. The self-described “picture writer” created more than 70 books for children, which combined sold 170 million copies. The most famous and most popular of his creations was “The Very Hungry Caterpillar.” The 1969 book, which had just 224 words, has sold 55 million copies. During an interview with NPR in 2007, Carle explained how his childhood provided the inspiration for his works.

“I think it started with my father. He took me for long walks and explained things to me.”

Carle’s idyllic childhood would quickly end as his immigrant parents decided to return home to Germany just before World War II.

Carle remembered being beaten by teachers and shot at by soldiers, and his beloved father disappeared into a Russian prisoner-of-war camp for years after being drafted to fight for the Nazis. The man who wrote The Very Hungry Caterpillar experienced hunger firsthand.

After graduating from art school, he returned to the U.S. and was hired by The New York Times. After a stint in the military during the Korean War, Carle returned stateside and went into advertising.

Carle wanted “The Very Hungry Caterpillar” to serve as an entry point for kids about to begin kindergarten. Michelle Martin, the Beverly Cleary Endowed Professor for Children and Youth Services at the University of Washington, told NPR the book helps little kids grasp concepts such as numbers and the days of the week, thanks to passages such as these.

“On Monday he ate through one apple. But he was still hungry. On Tuesday he ate through two pears, but he was still hungry.” 

In 2003, Carle received the prestigious Laura Ingalls Wilder Award (now called the Children’s Literature Legacy Award) from the American Library Association. It recognizes authors and illustrators whose books have created a lasting contribution to children’s literature.

Carle is survived by two children, Rolf and Cirsten Carle, and a sister, Christa Bareis.