13-year-old boy, Charley’s science fair partner, class “nerd,” crushing on Charley.

13-year-old girl, dreamer, violin player and self-styled modern-day Renaissance genius who loves all things STEM, Italy and Leonardo da Vinci. Modern-day Renaissance girl wannabe

13, social butterfly, smart but would rather be popular, Charley’s BFF (not!) and rival for Lex Campbell’s attention.

14, hot new guy at school, plays on baseball team and dreams of being recruited for major league team out of high school, major crush.

artist, scientist, musician, engineer and inventor during the Italian Renaissance. The term Renaissance Man (someone who does many things very well) was coined from Leonardo's many talents and is today used to describe people who resemble da Vinci

8-year-old girl in Renaissance Florence, works as an apprentice at SignoraVincenzo’s inn, and is the sister of Kairos.

13-year-old in 1492 Florence. Works in de Medici palace and takes the impetuous Charley under her wing to protect her from palace intrigue. She is Sra Vincenzo’s oldest daughter.

15-year-old who appears mysteriously at Charley’s dad’s office on Take Your Child to Work Day. He can travel across time to show up anywhere, any time. Kairos proves to hold the key to making her time machine work. Origins unknown. In 1492, he is Leonardo’s apprentice.