Here's why:

* Fine-grained refers to the texture of the rock, meaning the crystals are too small to be seen with the naked eye.

* Aphanatic comes from the Greek word "aphanes," meaning "invisible," and describes the lack of visible crystals.

Some examples of fine-grained igneous rocks include:

* Basalt: A dark-colored, fine-grained volcanic rock.

* Rhyolite: A light-colored, fine-grained volcanic rock.

* Andesite: A medium-colored, fine-grained volcanic rock.

It's important to note that the size of the crystals in an igneous rock is directly related to how quickly the magma or lava cooled:

* Slow cooling: Allows for larger crystals to form (coarse-grained or phaneritic).

* Fast cooling: Results in smaller crystals (fine-grained or aphanitic).