City research, and Player research.
The player research is basically learning new skills, such as "advanced constructions", "advanced medicine", and so on. But more about this later. Right now I am working at the City research.
Every city will be able to build various kinds of Research Labs. In the beginning, only one type will be available, but as new tech is discovered, additional, more specialized labs can be created.
Each research lab will have a researcher NPC, which will serve as a gateway between the players and the server.
Basically, each player has a certain number of research points, which replentish every day. The max number and the regeneration rate will be determined later, based on various attributes, state of health, and so on. Right now I am not worrying about this, but rather focus on the coding for the Research NPC.
So anyway, those research points can be used every day to the Research NPC to contribute to the advancement of various technologies.
Obviously, some technologies are dependent on previous tech, so you can't just start researching Cold Fussion when you are in the stone age.
Instead, you will have to research a lot of stuff first, such as the theory of atom, metals, nuclear reactors, fussion, particle accelerators, electricty, electomagnetism, cold fussion.
This is just an example, there will be a LOT more technology, and it should take at least 1 year for an average sized city to discover everything. In addition to that, various tech will require different research facilities. You can't research cold fussion in a herbal research lab. Instead, you'll need some sort of nuclear lab.