Leaf window, also known as epidermal window, is a specialized leaf structure consisting of a translucent area where sunlight can enter into the interior surfaces of the plant's modified leaf where photosynthesis can occur. This is also known as fenestration. The translucent structure may include epidermal tissue, and in some succulent plants it consists of several cell layers of parenchyma, which may also function as water-storage tissue. It can appear as a large continuous patch, a variegated or reticulated region, or as numerous small spots. This structural adaptation is found in certain succulent plants native to arid climates, which allow much of the plant to remain beneath the soil surface where it is protected from desiccation of extreme winds and heat while optimizing the absorption