Crystal Hubbard has penned picture books, contemporary and historical romance novels, and short stories. She is the author of Who Is LeBron James? and Who Was John Lewis? from the Who HQ series.

Maria Diaz Perera was born in Gijón, a small seaside town in northern Spain. When she was very young, she found out that there were few things in life that she enjoyed as much as listening to the Beatles and drawing. She graduated with a degree in art history and studied graphic design soon after. She has worked as a freelance illustrator for several international publishers, magazines, and advertising agencies and loves to work on portraits and children's books. She is very inspired by '60s and '70s music, literature, and cinema, and loves to spend time with her family and friends. She still listens to the Beatles and feels fortunate to be able to do what she loves most for a living, illustration.