Related Clues:

• Fermi's particle
• Very little bit
• Neutron's cousin
• Tiny source of energy
• It gets smashed
• Subject for Bohr
• Lepton site
• It's smaller than a molecule
• Bit of matter
• With 41-Down, nuclear device
• Bit to be split
• Democritus' indivisible unit
• Nuclear fission target
• Very small matter
• Molecule bit