Ever wonder what those strange floating things you see moving across your eye are? A recent Ted Ed Talk investigated the root of these very real objects known as "floaters," or muscae volitantes, and revealed that they actually aren’t tiny little organisms living in your eye, but rather your body’s own personal optical illusion.

Floaters are shadows of tiny objects inside the eyeball, whether they're red blood cells, clumps of protein, or bits of tissue. Their drifting movements may make them seem alive, but this movement is only because they exist in the jelly-like substance of the eye. When light enters the eye, the floater will cast a shadow on the retina, the light-sensitive tissue at the back of the eye. So, it’s actually the shadow and not the objects themselves that we see.

Another popular eye phenomenon many experience but hardly understand is the blue sky sprites, or the blue field entropic phenomenon. These are the tiny moving flashes of light that you may see dash across your eye when you look up at the blue sky on a sunny day. Unlike floaters, blue sky sprites are not shadows but rather tiny moving windows letting light into the retina. They are caused by white blood cells moving through the capillaries in your eye, creating “plasma spaces.”

Everyone experiences both floaters and blue sky sprites, although not in the same exact way. Since the brain is trained to ignore them, they generally go unnoticed. If your floaters are disruptive due to either their size or quantity, then it may be time to consult a doctor.