You must be very familiar with this picture, yeah i took this leaf wall structure with Foldscope a week ago. And this is so fascinating to see. You can see the asymmetric rectangle shape on the leaf structure. This is the Parenkim Parenchyma, elongated columnar-shaped cells (like the poles found on the tops of leaves) just below the upper epidermis of the leaf.
Do you curious about the function?
Parenkim Parenchyma contains many chloroplasts and it is used as a place to organize photosynthesis.