Related Clues:

• Tiny power unit
• Basic bit
• Bohr's study
• Bond component
• It was once thought to be indivisible
• Electron's place
• What's the matter?
• Particle
• It's little matter
• Half the dictionary?
• Powerful mite
• Something to smash
• Label on the first of two file drawers, maybe
• Lepton's locale
• Physicist's subject