What is the smallest object(s) that a Force user has manipulated?

Question

The movies and most other works seem to stress Force users by forcing(ha) them to manipulate large objects. Pillars, rocks, ships, etc... all large or pretty heavy objects. However, tiny objects provide their own challenges: namely being able to even identify them in the first place, and potentially being numerous.

What is the smallest object a Force user has been able to manipulate or influence in some way? I'm looking for separate answers for canon and Legends.

I seem to recall a (Legends) novel where a healing-focused student of Luke Skywalker manipulated individual particles while cleansing poison from the bloodstream of Mon Mothma, but it's been quite some time so I could be mis-remembering.

Answer 1

Legends

There are depictions in Legends of Force users manipulating microscopic objects.

One example is Darth Plagueis' manipulation of midi-chlorians in order to resurrect a person:

On the same day [Plagueis and Sidious] had allowed Venamis to die. Then, by manipulating [Venamis'] midi-chlorians, which should have been inert and unresponsive, Plagueis had resurrected him.

_{Darth Plagueis, p. 279}

We know that midi-chlorians are microscopic because we are told that

Midi-chlorians are a microscopic lifeform that reside within all living cells and communicates with the Force.

_{Qui-Gon Jinn, Star Wars: Episode I The Phantom Menace}

Another example, as mentioned in the comments by @BMWurm, is Cilghal's healing of a poisoned Mon Mothma by manipulating individual poison molecules with the Force.

It is not clear which of the two is smaller, though.

Canon

In canon I am unaware of any proven example of manipulating microscopic objects. As far as I can remember, the smallest objects that were manipulated in canon were lightsaber components while constructing a lightsaber:

(H/T @Politank-Z for the video link)

To get a sense of the size of lightsaber components, the schematic of Anakin's second lightsaber from Star Wars: The Visual Dictionary provides a good picture (H/T @WadCheber):

Sometimes small pieces of debris could be manipulated, even in combat -- such as when Darth Maul threw one to open a door in Episode I:

Note that it is possible Darth Plagueis succeeded in manipulating midi-chlorians in canon since Darth Sidious told Anakin that

Darth Plagueis was a Dark Lord of the Sith, so powerful and so wise he could use the Force to influence the midi-chlorians to create life

_{Darth Sidious (Palpatine), Star Wars: Episode III Revenge of the Sith}

However, this isn't a proven example since Sidious may have been lying. Plagueis may not have succeeded in resurrecting anyone because Sidious also told Anakin that

[Plagueis] taught his apprentice everything he knew, then his apprentice killed him in his sleep.

_{Darth Sidious (Palpatine), Star Wars: Episode III Revenge of the Sith}

Plagueis' apprentice was Darth Sidious, but Sidious later told the newly minted Darth Vader that

To cheat death is a power only one has achieved, but if we work together, I know we can discover the secret.

_{Darth Sidious (Palpatine), Star Wars: Episode III Revenge of the Sith}

Sidious therefore lied either in claiming that Plagueis had succeeded or that Sidious had learned the ability from Plagueis. Since Sidious never demonstrated the ability to resurrect others, it's possible he lied about Plagueis being able to cheat death -- especially since Sidious had a motive to lie about it in order to tempt Anakin.

Answer 2

Legends

The smallest objects that get moved with the Force would probably be the times in The Crystal Star (a Legends/EU novel) where the Solo kids move individual water and air molecules around.

Jaina rubbed some molecules of air together and created a faint light to work with.

[...]

Scared but determined, Jaina rubbed a few air molecules together to make a faint glow.

[...]

Jaina made some air molecules bump against each other. They made a soft humming, thrumming noise.

It seems probable that air or water molecules are smaller than the toxin molecules or microscopic organisms mentioned in other answers.

Canon

In Dooku: Jedi Lost (2019), a young Dooku manipulates grains of sand to force open a magnetic lock.

Answer 3

It was at the order of magnitude between 0,1 nm and 100 nm (nanometre).

As Null pointed out in his answer, in Legends canon, Plagueis managed to manipulate midichlorians. We don't know exactly how small midichlorians are, but we do know they reside in organic cells:

he was interested in observing the behavior of the Bith’s midi-chlorians as life ebbed. The Jedi thought of the cellular organelles as symbionts, but to Plagueis midi-chlorians were interlopers, running interference for the Force and standing in the way of a being’s ability to contact the Force directly.

Darth Plagueis, Chapter 1

According to random Internet post, the smallest organelle is ribosome; its size is 200-300 Å (20-30 nm). Biggest organelle, mitochondrion, is 100 times larger. For lack of better definition, I am going to assume that Midichlorians fall somewhere in that range; I am also going to give them benefit of doubt and assume they are closer to minimal value - let's say 10-100 nm.

I find it likely that you have to go below that to create holocron.

First, let's look at how holocron creation process was described in Darth Bane trilogy (emphasis mine):

He had made his first attempt five years before. Using Freedon Nadd's Holocron as a blueprint, he had re-created the intricate matrix of lattices and vertices that were the key to storing nearly infinite amounts of knowledge in a data system small enough to fit in the palm of a hand. It had taken months to gather and fashion the rare crystal into the filaments and fibers of the interlaced network, followed by weeks of delicate and painstaking adjustments. The matrix had to fall within highly exacting specifications, and Bane had spent hundreds of hours making thousands of precise, subatomic alterations through the power of the Force to ensure that each crystalline strand was properly in place.

Darth Bane: Rule of Two, Chapter 10

I am no crystal expert, but it seems that lattice is crystal structure and it is defined by position of individual atoms. Maybe bigger elements can constitute crystal lattice as well, but I guess bigger elements wouldn't require placement at "subatomic" level of precision.

We don't know what materials are used to create holocrons, but since they last for thousands of years and remain solid in environments habitable for humans, we can assume that this material can be found in periodic table.

Atoms size is extremely hard to measure and there are contradictory records available (in part due to fact that atoms do not really fall into our everyday definition of "size"). However, measurements are at order of magnitude of 0,1 nm (0,1 nm to 1 nm).

I summary, to create holocron, you have to move object with size of 0,1-1 nm.

This is ten to hundred times smaller than assumed size of midichlorians.

Answer 4

The smallest manipulation we know of in canon is electrons, which Palpatine manipulated to create the Force lightning in Episodes III and VI. (Force Lightning explained on http://starwars.wikia.com/)

Image from starwars.com

Smaller would require an understanding of quantum mechanics, which is beyond our ability as readers and writers to comprehend sufficient to find a viable use for. As such, I expect that there is nothing about this in current canon or Legends.

Note: Palpatine's Force lightning might have been created from something other than electrons, but my limited understanding of electric discharge indicates that the other options are much less likely and are on the same general order (protons, electrons, etc.).

Answer 5

In Legends canon, the smallest would be electrons.

Irek Ismaren was able to alter the programming of droids via the force

See this answer for details.

Answer 6

In Disney canon, the smallest example I could find that seems to be clear-cut telekinetic manipulation is either air molecules or water/liquid molecules. Either way, those things are pretty tiny. The following examples come from the Clone Wars TV series.

Season 1, Episode 10 - Lair of Grievous

A new Jedi Knight named Nahdar Vebb uses the Force to clear the fog that shrouds a building that they have tracked Nute Gunray to. The building turns out to be General Grievous's personal residence.

Season 2, Episode 18 - The Zillo Beast Strikes Back

With the Zillo beast running around on Coruscant, the Emperor Chancellor orders specially designed poison missiles bombs to be fired at the beast. Unfortunately, Anakin, Padme, Palpatine, Yoda, Aayla Secura, R2, and 3PO all happen to be in the vicinity at that time. So, the Jedi all use the Force on the gas or air to prevent the gas from encompassing them.

Season 4, Episode 3 - Prisoners

Kit Fisto, Anakin, Padme, and Jar-Jar are all on the Mal Calamari homeworld fighting the Seperatist army underwater. They are captured and Padme's helmet is intentionally cracked by their captor to pressure Anakin to reveal the location of the Mon Calamari Prince. Kit Fisto and Anakin use the Force to temporarily stop and reverse the leak in Padme's helmet.

There might be other examples, but those are the ones I've encountered thus far. But from these examples, the smallest objects a Force wielder manipuates is either N2 (nitrogen gas, assumes atmosphere composition in places such as Coruscant is like Earth) or H2O (water, assumes ocean composition in places such as Mon Cala is like Earth).