If you’ve ever taken a picture of your cat, you may be startled to notice that your cat’s eyes seem to glow extra bright as if your feline is possessed (it probably is). Fortunately cats are not possessed. Rather, the glow is called eyeshine.

Apparently cats have a layer of highly reflective cells located in the back of the eye behind the retina. These cells are called the tapetum lucidum and they act as a mirror that reflects light outward. Cats also have large eyes so that they can absorb as much light as possible. When you take a flash photograph of your cat, the light from the flash hits the tapetum lucidum and bounces back towards the camera, resulting in a green glare.

So feel free to take pictures of your cat, knowing it’s not capturing images of demonic possession. To learn more about how your cat’s eyes glow in pictures, click here.