The only layer of the epidermis where cell division occurs is the stratum basale, also known as the basal layer.

Here's why:

* Stratum basale: This deepest layer is where keratinocytes, the main cell type in the epidermis, are actively dividing by mitosis. These new cells push older cells upwards towards the surface.

* Other layers: The layers above the stratum basale (stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum) are made up of cells that are differentiating and becoming specialized, not dividing.

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