Many do not take kindly to the thought of eye boogers — those hard bits of crust that you wipe from your eyes when you wake up each morning. But you'd miss them pretty dearly if they weren’t there.

The complex wonders that are your eyes are coated by a three-layer tear film: the glycocalyx layer, made of mucus, which directly coats the cornea; a very thin, watery layer that helps spread the tears; and an oily layer made of meibum, which is secreted consistently by about 50 glands around the top rim of your eyelid and 25 glands lining the bottom one.

Eye boogers — technically known as rheum or gound but commonly referred to as sleepies or eye gunk — are a cocktail that is mostly meibum, with some parts mucus from the glycocalyx layer and other parts dirt and debris that you catch in your eye during the day.

Normally, you blink debris away during the day — and the older you are, the more you fight eye junk. Adults blink at a rate of about 20 per minute; babies only do it about twice per minute. (There are some studies as to why younger people are less inclined to bat an eye; one notes that babies have a "smaller eye opening and a thinner layer of fats and tear film," though what mattered more as far as blinking was concerned was whether the baby was engaged with an object or activity.)

Blinking protects the eyes by squeezing the meibomian gland, letting loose the oily secretion, and mixing all layers together to lubricate the entire system with the complex lipid and protein solution that makes up your tears. The act of fluttering your eyelids is also said to give your brain a miniature rest.

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When you sleep, your eyes remain shut, and as you rest, a mixture of debris is free to gather. The main meibum component, which is a liquid consistency at during the daytime, dries up because your body temperature drops slightly at night — enough to turn those tear-protecting oils into a solid.

Meibum has the important job of keeping your tear film from evaporating, and it also prevents tears from constantly streaming down your face all day (unless you're highly attuned to your emotions). Without sufficient meibum, you're left with dry eyes, redness, struggling vision, and an impressive used tissue mountain. Be thankful for the eye boogers.