Related Clues:
- Bit for 38-Across
- "We have split the ___"
- Supercollider bits
- Molecule building block
- With 4-Across, mushroom cloud producer
- Chemistry class models
- Very small bit
- Electrons' place
- Small parts
- Building block of nature
- Bond part
- One of three in a water molecule
- Microscopic building block
- Fermi's particles
- It has one or more shells