Why do cats' eyes glow in the dark?
For grown-ups: the science
Cats' eyes look like they glow because a shiny layer inside bounces nearby light back out.
Cats have a reflective layer behind the retina called the tapetum lucidum. It reflects unabsorbed light back through the retina, improving low-light vision and producing visible eyeshine when an outside light source is near the viewer's line of sight.
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Transcript
A cat peeks from a dim room, and its eyes look bright. Why do cats' eyes glow in the dark?
A cat's eyes take in even small bits of light from a lamp or the moon. That helps cats see when the room is dim.
Behind a cat's eyes is a shiny layer that bounces light back inside. The light gets another chance to help the cat see.
Some of that bounced light comes back out toward us. That is why a cat's eyes can look like they glow.
So cats' eyes are not making light. They are bouncing nearby light back toward us.