Anakin Skywalker: What are midi-chlorians?
Qui-Gon Jinn: Midi-chlorians are a microscopic life-form that resides within all living cells.
Anakin Skywalker: They live inside me?
Qui-Gon Jinn: Inside your cells, yes. And we are symbionts with them.
Anakin Skywalker: Symbionts?
Qui-Gon Jinn: Life-forms living together for mutual advantage. 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.
Anakin Skywalker: I don't understand.
Qui-Gon Jinn: With time and training, Ani, you will. You will.