Here's why:

* Prokaryotic cells are simple cells that lack a nucleus and other membrane-bound organelles. They are found in bacteria and archaea.

* Eukaryotic cells are complex cells that have a nucleus and other membrane-bound organelles. They are found in plants, animals, fungi, and protists.

The two cell types are fundamentally different in their structure and function, and there is no known mechanism for them to coexist within a single organism.

However, there are some examples of symbiotic relationships between prokaryotic and eukaryotic organisms:

* Lichen: This is a symbiotic relationship between a fungus (eukaryotic) and an alga or cyanobacterium (prokaryotic). The fungus provides structure and protection, while the alga or cyanobacterium provides food through photosynthesis.

* Human gut microbiome: The human gut contains a vast number of bacteria (prokaryotic) that play an important role in digestion and immune function.

It's important to note that while these examples involve both prokaryotic and eukaryotic organisms, they are separate entities, not individual cells within a single organism.