Midichlorian

Midichlorians are microscopic lifeforms in the Star Wars universe. They live inside cells of all living things and connect all living beings to the Force.

In the Star Wars universe, a higher number of Midichlorians in somebody means a stronger connection to the Force. People with high midichlorian counts can become Jedi or Sith if they are trained.

Midichlorians was first introduced in The Phantom Menace, where Jedi Master Qui-Gon Jinn noted an abnormally high Midichlorian count in a young Anakin Skywalker.  

Midichlorians do not automatically grant usage of the Force to someone. They allow them to hear the will of the Force and act through it. 

The idea of Midichlorians remains debated amongst Star Wars fans to this day. Some like the explanation behind how the Force works, while others prefer it to be left ambiguous.