Midi-chlorians were, along with Jar-Jar Binks, one of the most reviled additions of the Star Wars prequel trilogies. Their creation left fans wondering why George Lucas had to add a psuedo-science twist to his wizard space opera, especially one that meant the Force could only be used by a select few. Despite Liam Neeson’s kind and simplified delivery and Jake Lloyd’s guileless acceptance, the whole midi-chlorian concept felt a little clunky to many fans.
But what are midi-chlorians? According to George Lucas, who developed them in 1976, they are tiny microorganisms that are everywhere and that connect sentient beings with the Force. Lucas drew inspiration from two sources: the mitochondria, which is an organelle that resides within all living cells and that provides energy to them, and the Buddhist idea of a cosmic source of energy that powers everything in the Universe. Just like the mitochondria, midi-chlorians were once independent, but they chose to attach themselves to living organisms in perfect symbiosis.
Within the Star Wars canon, some sentient beings have a higher midi-chlorian count than others, and when it reaches a certain threshold, the lucky individuals can consciously access the Force itself. The Force contains both the mystical Cosmic Force that decides the movement of the stars and the destinies of civilizations, and the Living Force, which more concerned with the practical, operational and biological side of things. The midi-chlorians are firmly on the Living Force side, but they are able to connect with the Cosmic Force, which allows them to do pretty cool things.
First of all, midi-chlorians have a collective conscience and can communicate across the Galaxy. This means that although the smaller "colonies," for lack of a better word, that are attached to an individual behave a little bit like ants, they can emit and receive information from the hive-mind of the Galaxy, allowing the universe-spanning group to correct for the missteps of the individual.
The two most famous groups that deal with midi-chlorians are the Jedi and the Sith, both of which aim to control the Force in their own ways, which were completely opposed to natural reproduction. A powerful Sith called Darth Plagueis thought that he’d cracked the midi-chlorian code, allowing him to create life and to prolong his own through the usual Sith methods of torture, pain and absolute power. If midi-chlorians were sentient, wouldn’t they be able to use this new information to evolve enough to be able to create their own vessels, somewhere else in the Galaxy?
In the non-canon Expanded Universe, it was heavily hinted that Plagueis' sickening experiments to create life resulted in the same midi-chlorians that he tortured sending out the information and creating their own hospitable vessel, Anakin Skywalker, without having to wait for a father.
Lucas didn’t have time to introduce the concept of midi-chlorians in the original trilogy, so he introduced the idea in Star Wars: The Phantom Menace, where it tied in with larger themes about symbiotic relationships. In exchange from the privilege of living in the body of a human with an individual perspective, the midi-chlorians grant their chosen ones access to the powers of the Force. That’s why Anakin’s midi-chlorian count was so impressive. If so many Living Force midi-chlorians had chosen him as a vessel, his connection to the Cosmic Force must have been stronger than that of any other Jedi alive.
It's possible that the midi-chlorians who engineered Padmé’s unplanned pregnancy with Luke and Leia, which was a surprise to both parents. As the young couple said when they meet at the beginning of Revenge of the Sith, they had been separated for quite some time. That’s not to say that Anakin wasn't the father – rather than the mid-ichlorians living in him helped life find a way.
This perspective turns midi-chlorians from a shoe-horned attempt at introducing “serious” sci-fi into Star Wars to giving them a symbolic role that emphasizes how they tie the Galaxy together. In this context, midi-chlorians go from mitochondrial knock-offs to tiny tricksters that take advantage of the spectator’s disregard for them to ensure that the next generation of heroes gets to exist and thrive.
In The Clone Wars, Yoda visited The Wellspring of Life: a planet incredibly strong in the Light Side of the Force, which is possibly the source of midi-chlorians, with a clean desert surface that hides crevices where life flourishes in the most spectacular way. The connection that the midi-chlorians had to the Cosmic Force allowed Yoda to communicate with Qui-Gon Jinn and learn how to become a Force ghost -- another one of the useful tricks that midi-chlorians can grant to their hosts.
For a closer look at The Wellspring of Life, Deutsche Grammophon commissioned an animated Star Wars/Fantasia videoclip that takes place in a suspiciously similar planet, where "Across the Stars," the love theme that John Williams composed for Anakin and Padmé can be heard, tying the idea of midi-cholrians back to their relationship.
In the video clip, the Living Force appears as plants and creatures trying to survive. The Cosmic Force is the music itself, just like Leia recently explained to Poe, Rey, and Finn. Many of the motifs, plants, creatures and scenes that appear in the video are mirrors of events that have already happened or that will happen elsewhere in the saga: from the swamps of Dagobah to the shining kyber crystals infused with life or mother mushrooms protecting their children from the pouring rain, as they did in The Mandalorian trailer. It is the best (and fastest) visual illustration of why midi-chlorians are important: they are the smallest representation of the idea that, in Star Wars, size doesn’t matter, and it can be outright deceptive.
However, promoting life is not the only power that midi-chlorians have: the same ability that allows them to live a full life through an individual also allows them to help that individual come back as a Force Ghost, thanks to their connection with the Cosmic Force. This is partly how Qui-Gon Jinn, who was the closest thing to a midi-chlorian expert we’ve seen, was able to make a comeback and teach Yoda and Obi-Wan the same skill. And because these Force Ghosts are no longer tied to a physical body, but to the larger Cosmic Force that spans across the Galaxy, they can appear anywhere.
The third ability directly derived from midi-chlorians is more speculative, but there’s a case to be made that the same Living Force-Cosmic Force connection that makes them thrive is responsible for galaxy-spanning, instantaneous communication between Force Users like Luke and Leia or Kylo Ren and Rey. Snoke told them that he had “created” their bond in The Last Jedi, and it is believable, to a certain point, if midi-chlorian research was involved and he was privy to it. It would also explain, from a technical point of view, why the bond remained open after Snoke passed away; midi-chlorians are not slaves, but sentient entities with their own (collective) mind and a connection to the Cosmic Force, which is akin to a god in Star Wars.
These three powers (creating life, preserving individual spirits after death and communicating across the galaxy) put midi-chlorians at the heart of Creation itself, and turn them into a powerful storytelling tool that, in the right hands, could help to explore the more mystical themes of Star Wars from a ground-up perspective, just like the droid storylines tackle the philosophical topics of what it means to be human.
Although some fans might grumble at the idea and argue that Star Wars is not the kind of story that needs an explanation for everything, there are othe midi-chlorian lookalikes in two other massively successful science-fiction/fantasy franchises: Philip Pullman’s His Dark Materials presents the particle Dust of which everything is made, and that settles on sentient beings as they mature and evolve. Orson Scott Card’s Ender’s Game has Philotes, which are the basic building block of creation, and allow creatures to become sentient and can also allow for instantaneous communication across space through “twinning,” which sounds a lot like the bonding depicted in The Last Jedi.
As authors, Lucas, Pullman, and Scott-Card have extremely different religious beliefs, but the three of them have thought long and deep about spirituality, creation, love and destruction on a cosmic scale, as well as the idea of God itself, and have come to similar solutions to present their ideas to their audience. Pullman and Scott-Card chose a physics devices, and Lucas picked a biological organism, but how these tiny particles behave in their respective universes is extremely similar, and the taboos associated with them are almost the same.
Bad things happen when anyone messes with Dust, Philotes or midi-chlorians. The consequences range from creating massive holes in Pullman's multiverse to wiping out entire species in Scott-Card's word to turning the entire population of a planet mad in non-canon Star Wars. It’s akin to heresy, almost, which means that these tiny particle creatures act almost as physical manifestations of a universe-spanning god.
It's also interesting how these massive tragedies were that were created by messing with them could be healed in the three fictional worlds by individual acts of love and selflessness. It's difficult to say more without spoiling His Dark Materials or the Ender for new readers, but the restorative power of love, even after the most destructive acts have been performed, is another point in which the three authors coincide. It makes perfect sense from the midi-chlorian point of view: love is, after all, what tends to create and maintain life in the Galaxy, and ensure the midi-chlorians existence.
So although it will always be tempting to write-off or mock midi-chlorians, they're just another aspect of the Star Wars universe that symbolize some universal truth. And if nothing else, they're legitimately frightening creatures. Midi-chlorians are tiny, terrifying, omnipresent hive-minded gods able to get you pregnant when you’re alone, and capable of bringing loved ones back into your daily life from beyond the grave.