Related Clues:

• Possible solution
• ...
• Start of an invention
• Inventor's ''step one''
• Bright one from gray matter
• 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
• It comes to a head