Three short lines, and a whole world opens up. The poem begins with something small, a "little house," and then tells us it holds "a city / built of dirt." The surprise is in the scale. A house is where one household lives, while a city is crowded with many lives, streets, and buildings. The title, "Microcosm," points to the same idea: a tiny space that contains a larger world in miniature.
The poem never says what the little house is, so we have to imagine it. The word "dirt" suggests something humble, maybe a nest, a burrow, or a mound made of earth, though the poem leaves that open. What comes across is the speaker's quiet wonder. There is no complaint or argument here, just a person noticing and admiring. The mood is calm and attentive, with a little awe. The poem asks us to look closely at small, plain things and see how much busy life they might hold.