Juli Cabastini is the Science Nerds' chemistry expert and leader. She is 12 years old. She is like a scientist in a lab coat who loves mixing potions and making things change colours. She's always curious and loves experiments. She is kind of a mad scientist. Astra, aged 9, is her younger sibling and a Science Nerd. Juli is also friends with the Science Nerds Tim, Electro, Max, Chloe and Gizmo the robot. Juli's worst enemy is Josh.