The eyes of the cat glow at night because of the presence of tapetum lucidum. Tapetum lucidum is a membranous layer which is present in the eyes of the vertebrate and invertebrate species and is common in mammals. The tapetum lucidum is a reflective surface which causes the eyes of the animals to look like they are glowing in the dark. Human eyes lack tapetum lucidum. This located behind the retina. When the light enters the eye, the light rays bounce off the membrane. The presence of tapetum lucidum is responsible for the quality known as eyeshine in animals.