Midi-chlorian (Earth-2356)

"Without the midi-chlorians, life could not exist, and we would have no knowledge of the Force. They continually speak to us, telling us the will of the Force. When you learn to quiet your mind, you'll hear them speaking to you."

- Jiraiya, to Anakin Skywalker

Midi-chlorians are microscopic, intelligent life forms that originated from the foundation of life in the center of the galaxy, and ultimately reside within the cells of all living organisms, thereby forming a symbiotic relationship with their hosts. The Force speaks through the midi-chlorians, allowing certain beings to use the Force if they were sensitive enough to its powers. In order to gauge an individual's potential in the Force, blood tests are used to estimate the number of midi-chlorians within the subject's cells. Anakin Skywalker and Nagato, both considered to be the Children of the Prophecy at different points in time, possess some of the highest known count in galactic history—over 20,000 midi-chlorians—surpassing the potential of other legendary Force-users including Jedi Grand Master Yoda.

Source

 * https://starwars.fandom.com/wiki/Midi-chlorian.