Pym Particles (also known as Cross Particles) are subatomic particles of an extra dimensional nature that are capable of shunting or adding mass and reducing or increasing scale of any form of matter, compressing physical forces around such objects or organisms that they are applied to, as well as increasing density and strength of the subject. The particles were initially created in the 1960s by scientist Hank Pym, who aided the intelligence organization S.H.I.E.L.D. by harnessing the Pym Particles using a custom suit to become a field agent, alongside with his wife Janet van Dyne.
Despite Pym wanting to keep the Pym Particles a secret, Pym's former protégé Darren Cross managed to successfully recreate the Pym Particles in 2015, using it to create the Yellowjacket Suit, which he planned to sell to terrorist groups such as HYDRA and the Ten Rings.
Human users of technologies that harness the particles are able to shrink themselves to the size of an insect, while still possessing the physical resilience, as well as effort and force exertion capabilities of an average-sized human, which can be amplified in their reduced scale.
The process of altering size compresses force and energy, manifesting as brief shockwaves of vibration around the target, which enhances the amount of force the target can generate. It also enhances the density and resilience of a target, making them stronger and harder than normal. Living subjects of this develop inhuman effort and exertion capabilities, notably giving them the force of a bullet while shrunk.
During the 1960s, Hank Pym discovered and isolated a rare group of subatomic, extra-dimensional particles, which became known as "Pym Particles," that could increase or decrease the size and mass of objects or living beings by shunting or adding it from a subatomic dimension. He formulated the particles inside a special suit designed to harness them and that allowed him to shrink down to the size of an insect.
He and his wife Janet van Dyne used these abilities to become the S.H.I.E.L.D. enhanced operatives, codenamed as Ant-Man and the Wasp. However, a tragic incident occurred during a mission to defuse a missile attack. Van Dyne used the Pym Particles to shrink to a subatomic level, which resulted in her disappearance into the Quantum Realm. This caused Pym to abandon the particles and his heroics, swearing to never let anyone get a Pym Particle as long as he's alive.
In the meantime, Pym founded his own company, Pym Technologies. He was ousted out of his company by Darren Cross and became concerned that he was intending to recreate his Pym Particles and utilize its shrinking ability to market his weaponized Yellowjacket Suit. Eventually, Pym was forced to recruit a new Ant-Man and teach him how to use Pym Particles so that they could complete their mission to stop Cross from selling his own version of the Pym Particles, dubbed "Cross Particles," to nefarious organizations.
When Scott Lang reemerged from the Quantum Realm in 2023, he brought the Pym Particles he had left to the New Avengers Facility. He warned Hulk to be careful when he was inserting a vial of Pym Particles into a new Quantum Realm Exploration Suit as they only had a limited supply since Hank Pym was killed in the Snap and therefore they were unable to make more. Lang noted that he had enough for one roundtrip per member and an extra two for test runs but accidentally wasted one.
During the Time Heist, Tony Stark and Lang botched the attempt to get the Tesseract. After being reminded by Lang that they only had enough to go back home, Stark realized that they could go back further to a point where the Tesseract was still in the possession of S.H.I.E.L.D. and Pym was still working with S.H.I.E.L.D. so extra particles can be retrieved. Stark and Captain America traveled to Camp Lehigh on April 7, 1970 while Lang returned to the present with the Mind Stone. In the S.H.I.E.L.D facility, Rogers was able to get Pym out of his lab by making a call regarding a package for him. Rogers was able to infiltrate his lab and got more Pym Particles for the trip home.
In an alternate 2014, Nebula was captured by Thanos after she and War Machine stole the Power Stone. She was held prisoner on the Sanctuary II by her past version of herself and Gamora. Her vial of Pym Particles was taken by Ebony Maw, who created more of them so Thanos and his army could go to 2023 to face the Avengers.
Pym Particles have the capability to alter the scale, mass, strength, and density of organic and inorganic subjects, most notably to reduce them to the size of an insect while retaining their normal strength density, enhancing it as the subject shrinks. In reduced scale, a subject is enhanced by enhanced density and strength, as well as compressed energy and physical force of the subject, which results in an organic subject to possess unnaturally high levels of physical effort and exertion capability and also astonishing strength and durability. This is done by adding or shunting mass from a subatomic dimension from which the particles gain their abilities.
The process of altering the size and changing mass levels results in extreme physical forces being created and dramatically increases the momentum of an organic subject. Such force can be exerted immediately after changing size. This further increases the physical effort capabilities, as well as the strength and durability, of organic subjects which they can use to perform feats of inhuman physical exertion and strength with similarly inhuman ease; especially right after a human subject uses it while returning to normal size. One example is if a human user is falling from a great height in their small scale, they can utilize the kinetic energy and momentum obtained from falling and exert this force immediately after or while returning to normal size. This will translate as a feat of inhuman strength while in normal size.
The Particle's ability to warp mass and size can transport said mass, and also objects and living beings, into what is known as the Quantum Realm, a subatomic dimension of space that holds any mass of those who have shrunken with the use of the Particles. The mass, while still part of the shrunken subject, is shunted inside the Quantum Realm until returned. As the blue Pym Particles Disks have demonstrated, mass can be added onto a subject of the Particles and allow the subject to increase their size rather than shrink it.
There are two types of Pym Particle serums: blue and red. They are used to power the Ant-Man Suit but the red serum also powers the Yellowjacket Suit and the Wasp Suit. They are also used to weaponize Pym Particles Disks. As the effect shown when the disks hit its targets:
- Red Pym Particles shrinks and gives increased strength.
- Blue Pym Particles enlarges thus growing mass and gives increased strength and weight as depicted by the enlarged Thomas the Tank Engine toy and the ant that Cassie Lang kept as a pet.
There can be negative side effects with the use of Pym particles without safety measures. Being exposed to and using Pym Particles over a protracted period of time can cause extreme levels of mental instability, as it alters the chemistry of the brain. Hank specifically designed the Ant-Man Suit's helmet to protect the user from this suffering brain damage while using the particles.
The Pym Particles seem to have an adverse effect onset after continuous use on humans. Without proper protection such as the Ant-Man Suit, humans turn into a protein goo outright. Even with the protection of the suit, Hank Pym stated that continuous use of the suit had taken its toll and thus further using the suit and shrinking could cause some hazardous health problem to him.
Also, forcing to shrink after a certain threshold, such as deactivating the regulator on the suit that limits the user from shrinking beyond the size of an insect, will cause the user to continuously shrink until they reach a point where they become subatomic and reach the Quantum Realm. At that point, time does not hold any sway and concepts of space are irrelevant. Once there, they will be frozen in time, unable to age, but also be in a state of unconsciousness or half-consciousness, barely aware of their surroundings. They can try to fight this, but they will eventually succumb to it and be unable to act. Scott Lang found the will to fight the effects of the Realm, as sound could still travel through it and he was able to hear calls of his daughter a few feet away from the point of where he went subatomic. His daughter's calls motivated him to find a way to restart his regulator by inserting an enlarger formula disc into it and switching it back on, thus allowing the enlarging controls on his suit to work again. This allowed him to return to his normal size, but he could not remember what happened while he was inside the Realm. Pym theorized that the human mind could not comprehend the experience.
Using the Particles to become giant also seems to cause a large amount of physical strain to the user. The Ant-Man suit's "Giant Man" function seems to require manual activation and Scott Lang was visibly exhausted and strained after using it for only a few minutes. He also mentioned that the first time he activated the function he was "nearly split in half". His use of the "Giant Man" function during the Chase for the Mobile Laboratory ended with him collapsing due to exhaustion; Hope van Dyne was forced to shrink Lang manually to prevent him from drowning in the San Francisco Bay.
Using Pym Particles to travel across time through the Quantum Realm is also highly volatile. When Hulk ran a time travel test on Scott Lang, Scott was repeatedly aged and deaged uncontrollably.
Pym's former protégé Darren Cross worked for years to try to recreate shrinking technology on his own but grew upset as he slowly realized that Pym always possessed the technology but had hidden it from him. Cross's research eventually developed to the point that he could shrink inanimate objects, but trying to shrink living organisms reduced them to miniature piles of goo. After a great deal of trial and error, however, Cross was able to develop Cross Particles for use in the Yellowjacket Suit, which were stable enough that they would not kill a human being in the shrinking process.
While the perfected Pym Particles used by Hank Pym were red when in a suspended solution, Cross's Cross Particles were yellow. While they came close to matching the functions of Hank Pym's version of the technology, they lacked certain refinements that Pym had made to counteract health damage caused by prolonged exposure, i.e. altering the brain chemistry and leading to mental instability.
Exposure to the Cross particles made Cross increasingly unhinged, and he eventually revealed that he intended to sell the technology to HYDRA. While Cross was stopped by Ant-Man, and his laboratory destroyed along with all computer files, S.H.I.E.L.D. turncoat and HYDRA representative Mitchell Carson was able to flee with a sample of the Cross Particles.