system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do eyelids randomly start twitching for a few seconds?
gpt
This phenomenon is called a fasciculation. It is caused by a spontaneous action potential, which makes the muscle contract involuntarily.

It actually happens in every muscle in our body, but other muscles are too big and the area it happens is less sensitive so we are less likely to notice it!