system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why does our face look different after we wake up?

And how does it change back to normal?
gpt
When you lie down at night, fluid accumulates in your head more than usual because gravity is no longer pulling it down back into your body. This causes a little bit of swelling or puffiness in soft tissue like your face. When you get up in the morning and are upright again, it takes a little while for gravity to drain the fluid levels back to your normal upright equilibrium.