Guillaume Federighi, aka Hey Gee, is a French and American author and illustrator. He began his career in 1998 in Paris, France, and spent time exploring street art and graffiti in several European capitals. Since moving to New York in 2008, he has worked with many brands, developing a reputation in graphic design and illustration for his distinctive style of translating complex ideas into simple and timeless visual stories. He is also the owner and creative director of Hey Gee Studio, a full-service creative agency based in New York.

Weston, age 12, plays goalie for a traveling soccer team and also enjoys biking and climbing. When he's not at practice, games, or activities with his family, he likes to play the trombone, read, make art, and play virtual reality games. He was diagnosed with hemophilia shortly after birth and had a port in his chest for many years to receive treatment with clotting factors. Now, with a newer treatment, he gives himself injections every 28 days and no longer needs the port. He lives in Rochester, Minnesota, with his parents and brother.

Rajiv K. Pruthi, M.B.B.S., is the director of the Hemophilia Treatment Center and co-director of the Special Coagulation and Molecular Hematopathology Laboratories at Mayo Clinic in Rochester, Minnesota. A leading expert on diagnosis and treatment of coagulation disorders, his research focuses on advancing translational science in these areas to improve care and quality of life. His work has helped to keep young patients in school and keep older patients from missing work through advances in reducing hospitalization. Dr. Pruthi has also received numerous awards for excellence in teaching as a professor at Mayo Clinic College of Medicine.