There’s honestly no better feeling than collapsing into bed after a long, exhausting day—your head hits the pillow, and before you know it, you’re off in dreamland.

But waking up? That’s a different story. Nothing kills the morning vibe faster than stumbling to the mirror and spotting that weird, yellowish gunk stuck in the corners of your eyes.

Most of us are so used to it that we just wipe it away and move on, pretending our bodies aren’t doing totally gross stuff while we sleep. But ever wonder what that “eye crust” actually is?

Well, after a TikTok video went viral breaking it down, people were seriously stunned.

“If you have ever woken up in the morning and you have some crust on your eyes,” explains Andrew Huberman in the video, “And you know that crust, that kind of yellowy stuff—sometimes it’s yellow, I know this is kind of gross.”

He goes on: “That’s actually dead bacteria that your eyes have successfully defeated during your night’s sleep.

“So when you wipe those away, you’re taking the casualties of a war that you won during your night’s sleep and you’re whisking those away.”

Yep, you read that right—your eye gunk is basically your body’s little victory trophy from a microscopic battle that happened while you were snoozing.