The tapetum lucidum is a layer of tissue located behind the retina in the eyes of many animals, including cats, dogs, and deer. This structure reflects light that passes through the retina back into the eye, enhancing night vision by allowing photoreceptor cells to capture more light. This adaptation is particularly useful for nocturnal animals, enabling them to see better in low-light conditions. The tapetum lucidum is responsible for the characteristic glow seen in animal eyes when light shines on them at night, often referred to as "eye shine."