What word that means very small?

There are many words that mean "very small," depending on the specific context. Here are a few options:

General:

* Tiny

* Miniature

* Petite

* Diminutive

* Microscopic

Specific:

* Minute (extremely small)

* Infinitesimal (extremely small, almost impossible to measure)

* Subatomic (smaller than an atom)

* Nanometer-scale (measured in nanometers, a billionth of a meter)

* Fractional (a small part of something)

The best word to use depends on the specific context and the size you want to convey.