Related Clues:

• Brain waves
• Inventor's ''step one''
• Bright one from gray matter
• They're sometimes funny
• Inventor's start
• Light bulb's signification, in cartoons
• Light bulb, in comics
• Mental glimmer
• Object of thought
• Head piece?
• Creator's sine qua non
• Brainchild
• Theory
• Lightbulbs, in the comics
• It comes to a head