Development of the character Percy Jackson began when Rick Riordan started inventing stories for his son Haley Riordan, who was diagnosed with ADHD and dyslexia in the spring of 2002. When Haley was in second grade and he was studying Greek mythology, he asked his father to tell him bedtime stories based on those myths. When his father ran out of ideas, Haley suggested that he make up new stories that combined existing mythological characters with new ones. This led Riordan to create the fictional character of Percy Jackson and the story of his travels across the United States to recover Zeus's lightning-bolt. Haley then[when?] suggested it be written as a novel. Riordan received input on the manuscript from some of his middle school students before taking the idea of Percy Jackson to a publisher.