False-colour scanning electron micrograph of the under surface of a leaf, Zinnia elegans, showing a part of the epidermis removed to reveal the spongy mesophyll layer (left) under the surface. The epidermis (right) consistis of large, irregular cells with waterproofing constituents in the wall. The jigsaw effect corresponds to the epidermal cells. The epidermis shows stomatal pores, which regulate the exchange of air between the atmosphere and the leaf's interior. Mesophyll cells are large and attached at limited points only, creating airspaces through which the air entering via the pores circulates freely through the leaf. Magnification: x150 at 6x4.5cm size.