microcosm

Short definition from Wiktionary

Noun

1. 1
   Human nature or the human body as representative of the wider universe; man considered as a miniature counterpart of divine or universal nature.
2. 2
   The human body; a person.
3. 3
   A smaller system which is seen as representative of a larger one.
4. 4
   A small natural ecosystem; an artificial ecosystem set up as an experimental model.