Why did my eyelid start to twitch?

Mild twitching of the
eyelid is a common phenomenon. Although these involuntary contractions of
muscles are annoying, they are almost always temporary and completely harmless.
The medical name for this kind of twitching is ocular myokymia. It is quite common
and most often associated with fatigue. Usually when your eye is twitching, it
is not visible to anyone else.

How can I make it stop?

 Optometrists and
ophthalmologists often are asked what causes the twitching and what can be done
to stop it. Lack of sleep, too much caffeine or increased stress seems to be
root causes. Often, gently massaging your eye will relieve the symptoms.
Usually, the twitch will disappear after catching up on your sleep. In extreme
cases, Botox can be used to calm the muscle.