Even at a time of augmented reality and Internet access provided by the very clothes they wore, most people didn't really understand what a micro-factory was. Most assumed they were some sort of universal constructor, taking in blocks of raw material, and spitting out whatever the client asked for. This idea is nowhere near correct, but at the same time, not wholly wrong.
Microfactories are meant to increase the gestalt efficiency of society. While an arcology brings people together to reduce transit energy needs, Micros centralize component manufacture. One factory can produce car bodies, art deco furniture, or staplers - all it needs is the correct template and a supply of material. Although a single unit the size of a three story office building might not produce much, multiple units can be brought together.
Nanotechnology Fabrication Laboratory
(NFLab, Nano-Factory, Nanofac, Grey Goo Cauldron)
Nanofactories use nearly microscopic robots to work on ultra-small scale components. This variety can create new materials, computer components, specialized power cells, certain medicines, high quality lenses, and many other objects that require exacting detail of workmanship.
Generally speaking, a nanofac doesn't produce things much larger than a paperback book. For all of its utility, nanorobtics doesn't function that well for most things. Imagine trying to construct a toothpick from specks of sawdust instead of turning a log into veneer and then slicing into thin bits, and the bottleneck becomes obvious.
NFLabs are are quite rare, despite being the general publics' image of small scale fabrication. They are extremely expensive to run as the miniature robots must be kept in sterile, temperature controlled facilities, constantly monitored, and the throughput is not particularly high. Specialized feedstock must be imported, due to the danger of universal deconstructors.
Deconstructors are possible, and used to prepare the feed stock for more general factories. However, these units are kept well guarded, and generally not advertised. Something that can reduce just about anything to its component molecules is obviously best kept secure.
Automated Limited Materials Working Facility
(ALM-Fac, Work Box, Micro-Fac)
These are the far more common type of micro-factory. The inside of each house sized structure is a combination three dimensional printer, fabrication shop, and deathray. Plastics and epoxies are set down in layers and melted together in intricate patters, while lathes and grinders shape other materials.
The key piece of technology in these types of factories is not tiny robots, but giant lasers. Depending on how they are focused, these can cut, weld, heat, or etch, and yet never need sharpening. Except in specialized cases, this means that one tool can work with any material within, a series of mirrors shunting the beam to where its needed.
MicroFacs are specialized, but can work near miracles within expertise. For example, a fabric work box can make chemical agent resistant battle dress uniforms, silk evening gowns, and silk evening gowns, and bullet proof vests, more or less concurrently. Metals, wood, and organic based plastics are some of the more common types, though almost anything can be created. There are indeed liquid chemical handling factories that can produce pesticides, shampoo, or any number of other products. Furthermore, multiple work boxes can be strung together with automated conveyors to let them share products and work in stages.
Although there are access ways, most of these units are not designed to have humans on the manufacturing lines. A control center and break room are present for the people to oversee the operation, and affect the occasional repairs.
The true key to all of these factories are heavily encrypted Computer Aided Design files. As stated several times before, the microfacs are designed around materials, not the end product.
Security and encryption are paramount, given that a factory could easily be re-purposed for weapons manufacture or other malicious deeds. The designs are stored their own programing language on special disks that are required as a dongle. These units often have manufacturing caps or other built in limitations to protect intellectual properties and prevent copying.
Post event, it is often the templates that are harder to find than the factories themselves.