Ribosomes do their work in the cytoplasm of a cell. More specifically, they can be found:

* Free-floating in the cytoplasm: Ribosomes that are free-floating in the cytoplasm typically synthesize proteins that will be used within the cell itself.

* Attached to the endoplasmic reticulum (ER): Ribosomes attached to the ER synthesize proteins that will be secreted from the cell, packaged in organelles, or embedded in the cell membrane.

So, while ribosomes are not confined to a single location, they primarily function within the cytoplasm.