a small world; a microcosm
Refers to a small, self-contained world or a miniature version of a larger system. Often used metaphorically for a close-knit community, a specialized field, or a personal realm.
This village is a small world apart from the city.
His laboratory was a microcosm for him.
Compound of 小 (small) + 天地 (heaven and earth, world). The combination literally means 'small heaven and earth', i.e., a small world or microcosm.