Related Clues:

• Infinitesimal or tiny amounts, say, principally
• Bohr model subjects
• Bits of chemistry?
• "Iliad" characters
• One ordinary seaman penning thank you letters
• Holes in the wall plugged by round building blocks
• Homes of protons
• Scraps of paper I'm obliged to include in sort of map
• They can't be trusted because they make everything up!
• Building blocks in chemistry
• Small matters?
• Building blocks smaller than Lego
• There are trillions of them in a speck of dust
• Little letters?
• They're next to nothing (except thetas and kappas!)