This schematic cross section shows the main elements of a foliage leaf.

The outer-most cell layer (epidermis, marked in brown colour) is covered on the outside by a waxy stratum (cuticle, marked in red colour). The cells between the two outer layers contain chloroplasts, which are responsible for photosynthesis, (marked in green colour), constituting the densely packed palisade parenchym and the loosely packed mesophyll. The internal air space of the leaf is connected to the external air via the stomata (marked in blue colour).