Related Clues:

• What you need first to make an invention
• ''What's the big __?''
• Brilliant thing to come to mind
• It's a great thought
• Big, bright or silly thing
• What a lightbulb represents, in comics
• Matter for gray matter
• What a would-be inventor needs
• Flash of mental inspiration
• It may be half-baked in one's brain
• What you first need to invent something
• Cogitation creation
• 'I have no ___'
• Some provide aid in theory
• Internal impression