Microcosm definition

From the French microcosme, from the Latin microcosmus, from the Greek μικρός "small" + κόσμος (kosmos) "world"

a smaller system which is representative of or analogous to a larger one

Though our town is small and provincial, it is a true microcosm to the country as a whole.
a small, complete world
- 1608: If you see this in the map of my microcosm, follows it that I am known well enough too? — Shakespeare, Coriolanus, ii 1

The plural of this word is rarely used.