Microbots, invented by super genius Hiro Hamada, are micro-sized robots capable of forging together in order to manifest themselves in whichever shape or function the creator has the mental capacity to command via neural-cranial transmitter.
Despite being used for a good purpose, Robert Callaghan steals and starts controlling them, using them as a dangerous weapon.
A Microbot is black in coloration and resembles a diamond shard no larger than a nickel. But thanks to their size, they are incredibly versatile; by binding with each other via electromagnetic connectors, together they can move, build, and adapt to any situation and evade damage as well as supply reinforced strength.
Microbots are designed to connect together to form various shapes and perform tasks cooperatively. They are all controlled by a single neural transmitter, and whoever wears it can command the Microbots to respond by a thought. All Microbots are designed to operate at high efficiency, even if the controller does not command the Microbots to do so.
However, a critical weakness that the Microbots contain is their quantity: Microbots cannot self-replicate and must be manufactured in large amounts to be able to perform heavy tasks or complex, solid formations. Without enough of their own for support, Microbots are vulnerable to attacks and each can quickly fall due to the fragility of their miniature size.
Hiro tries coming up with a good invention to be admitted into the San Fransokyo Institute of Technology, but cannot come up with anything good until Tadashi holds him upside-down, so he looks at Megabot and the idea of Microbots comes to his mind. Soon, Hiro begins mass-producing the robots with the help of Tadashi and his friends, Go Go Tomago, Honey Lemon, Wasabi and Fred, taking many days and nights to create enough.
In a supplemental comic called "Tech Nightmare" it is shown that during this time, Hiro waited for Tadashi's friends to rehearse the project, but fell asleep with the neurotransmitter on. However, when the gang arrived, Hiro began subconsciously attacking them because he was apparently dreaming of bot fights. He was then waken up by Honey Lemon, but they all decided to go away instead when Hiro offered to demonstrate the Microbots.
Much later, Hiro and company go to the SFIT to showcase their invention, but Hiro is nervous at first so not many people seem interested. Thanks to Tadashi though, Hiro got confidence and impressively showed the bots' capabilities to build and transport, and at the end, everyone cheered him. Alistair Krei then approached Hiro and his family, seeking to buy the bots, but Professor Callaghan tells Hiro not to do it, showing disdain for Krei. Krei however tried to take one microbot away, but Tadashi notices this and tells him to return it. Krei acts as if he was unaware he had it, and gives it back to then leave. Not long after the presentation, a mysterious fire is caused in the building while the Microbots were still inside, and Tadashi tries going inside after he is told that Professor Callaghan was still in the building. Unknown to anyone, it was Callaghan who had started the fire and shielded himself with the Microbots to fake his death.
Tadashi still goes inside; but unfortunately, he dies after an explosion and the Microbots are all seemingly destroyed as well. This causes Hiro to become depressed for the following weeks, until he hurts his foot and activates Tadashi's healthcare robot, Baymax.
Baymax notices that a Microbot is still active, but Hiro thinks it might just be malfunctioning and encases it. Baymax then decides to investigate where the Microbot is trying to go, as he thinks it will make Hiro feel better. Hiro, feeling responsible for the robot and not wanting it to get hurt, tries to catch up with him and follows all over town until they arrive to an abandoned warehouse. Both go inside and Hiro not only finds that his Microbots survived, but more were being created as well. Before they get the chance to do anything, a mysterious masked man begins attacking them with the bots, but Hiro and Baymax manage to get away.
Hiro and Baymax go to the police station to report this but their story seems too far fetched for the officer attending them, and Baymax's battery gets low so they just go home instead. Still, Hiro thinks something must be done about the mysterious man and begins to theorize that he might have caused the SFIT fire that killed Tadashi, so he gears up Baymax with a combat chip and a fighting armor, then both set off to the warehouse again, only to find that the masked man had left. The encased Microbot then begins acting up once more, so Hiro follows it until they arrive to the bay, where they meet Go Go, Wasabi, Fred and Honey Lemon after Baymax had contacted them to make Hiro feel better.
The masked man then tries killing the team, and follows them while they escape on Wasabi's car by using the Microbots for transport. Finally, he almost traps them but they fall to the ocean instead, so he leaves them there believing they had perished. The gang however survive and all of them decide to join Hiro in arresting the villain so they can avenge Tadashi, so Hiro gives them battle suits as well.
They plot to take off the Kabuki mask from him, which was attached to the neurotransmitter controlling the Microbots, and then go to Akuma Island after Baymax had detected his vital signs there. The team enter an abandoned facility and engage in a fight with the villain, but he proves to be too skilled with the Microbots and overwhelms them. He however has the mask taken off, and it's revealed to them that it's none other than Robert Callaghan. Hiro becomes enraged as he believes Tadashi died for nothing then, and tries murdering Callaghan by taking off Baymax's healthcare chip, thus only leaving his "killer" mode on. Callaghan escapes as the rest of the team stop Baymax, telling Hiro that murder was not the plan nor the answer, and after they make amends, go out to stop him again. They see that Callaghan had gone to Krei Tech, as his plan was to take revenge against Alistair Krei for supposedly having his daughter die in the Silent Sparrow project, and used the Microbots to recreate the portal from the project and suck everything Krei loved inside it to be lost forever.
The team of heroes soon arrive to battle Callaghan, although they still are easily beaten by him until Hiro realizes what must be done, so he orders his teammates to destroy the Microbots and have them sucked into the portal because then Callaghan would have nothing to control. They manage to do this, thereby succeeding in stopping Callaghan and getting rid of all the remaining Microbots.
- In the manga of the film, the bots can join together to create and form large, black animals like spiders, apps and even a dinosaur.
- Hiro's superhero emblem in Big Hero 6 is two Microbots forming an "H".
- The Microbots appear in Disney Crossy Road as road obstacles.
- In Big Hero 6: Bot Fight, Microbots appear in 5 different types: Hydro, Bio, Thermal, Solar and Magnetic. Unlike the film's Microbots, they have Megabot's face, and can evolve into Megabots. In turn, these Megabots evolve into Macrobots, which also resemble Microbots.