"Three part cells" is not a standard biological term. Cells are generally classified based on their internal structure and function, and the number of parts is not a common classification criteria.

Perhaps you are thinking of:

* Eukaryotic cells: These cells have a nucleus and other membrane-bound organelles, which could be considered "parts."

* Prokaryotic cells: These cells lack a nucleus and other membrane-bound organelles, but they still have distinct parts like the cell membrane, cytoplasm, and ribosomes.

If you could provide more context about the cells you're referring to, I can provide a more specific answer. For example, what kind of cell are you interested in, and what are the three "parts" you are referring to?