Related Clues:
- 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
- Charged subatomic particle
- Minute matter
- It's split in a lab
- Quantum mechanics model
- Elemental combiner
- Basic unit of matter
- Bit of negativity?