Itsy-bitsy bits WSJ Crossword Clue

Think of the tiniest building blocks that make up everything around you.

????? are the basic units of matter and the defining structure of elements.

The clue 'Itsy-bitsy bits' suggests something extremely small, as 'itsy-bitsy' is a playful way to describe something tiny. 'Bits' implies fundamental components or parts, which leads to '?????,' the basic building blocks of matter.

Nuclear reactors split them, A water molecule contains three of these, Itty bits, There are roughly ten million billion (10^16) of these in a grain of salt, Tiny particles