If you are trying to answer "lego" for the "little building blocks" clue in the NYT Mini Crossword, stop right now. That was my first guess, but it doesn't work. This clue isn't about literal building blocks, but about one of the tiniest particles that make up our world. Here are some hints.

The basic particles of the chemical elements.

Is an anagram of “TOMAS”.

_____ molecules form by bonding.