system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does our eyelids form crystal like substances while we sleep?
gpt
Tear ducts lubricate the surface of the eyes occasional dust and other minute particles reach the surface of the eye, these are then blink washed away a bit like a windscreen wiper. This material then accumulates at the edges where some of the liquid evaporates leaving behind the solid material.