There’s an interesting story behind that little bit of pink conjunctival tissue you see out of the corner of your eye. While you may have paid a lot more attention to it while doing your makeup, these pink bits called the plica semilunaris are responsible for helping with tear drainage and eyeball mobility.But in the past, they were part of a third eyelid that functioned to protect and moisten the eye. This third eyelid is still present in cats or dogs, but for humans, it evolved a long time ago, and now we only have a vestigial bulge of tissue, that’s the one we see in the corner of our eyes.