I was born in 1952 in Hickory, North Carolina. My father, who would become a physics professor and astronomer (and recently my co-author on a book about the Solar System), was in the military and, later, working on science degrees at several different universities. We moved often. I lived in North Carolina, Panama, Virginia, Kansas, and Colorado. Wherever we lived, I kept a menagerie of lizards, turtles, spiders, and other animals, collected rocks and fossils, and blew things up in my small chemistry lab.

Because we moved often, I didn't have a large group of friends, and I spent a lot of time with books. My parents read to me until I could read myself, and I became an obsessive reader.

My interest in science led me to believe that I'd be a scientist myself. At the last minute, I chose instead to go to art school in North Carolina, where I studied graphic design. After graduation I moved to New York City, where I worked in advertising and design, first in large firms and then with my wife, Robin Page, in our own small graphic design firm. Robin, also an author and illustrator, is my frequent collaborator — we've made sixteen children's books together.

Our daughter Page was born in 1986 and our son, Alec, two years later. We began reading to them when they were just a few months old, and I became interested in making children's books myself. My wife and I read to our two older children almost every night until my daughter was 12 or 13, long after they were reading on their own. It was, in many ways, the best part of the day.

In 1994 we moved to from New York City to Boulder, Colorado, where we work in a studio attached to our house, which was built in the 1880s and often functions as if it were still the 19th century.

Our youngest son, Jamie, was born in 1998. The questions my children asked over the years have been the inspiration for many of our books.