The cells between the upper and lower epidermis of a leaf are called mesophyll cells.

Here's a breakdown:

* Epidermis: The outer layers of the leaf, providing protection.

* Mesophyll: The tissue in between the epidermis layers, responsible for photosynthesis.

Within the mesophyll, there are two main types of cells:

* Palisade mesophyll: These cells are elongated and tightly packed, located near the upper epidermis. They contain a high concentration of chloroplasts, the sites of photosynthesis.

* Spongy mesophyll: These cells are irregularly shaped with large air spaces between them. They are located near the lower epidermis and facilitate gas exchange for photosynthesis.

Let me know if you have any other questions about plant anatomy!