{i} layer of cells in a developing sporangium (Botany); membranous layer (Anatomy, Zoology)
An area in the pigmented layer of the choroid coat of the eye in many animals, which has an iridescent or metallic luster and helps to make the eye visible in the dark
A layer of tissue in the eye of many vertebrate animals, immediately behind or sometimes within the retina, that reflects visible light so as to increase the light available to the photoreceptors