A microcosm is the smaller parts of a system, usually referring to a smaller part of the cosmos.
A macrocosm is the larger whole of a system, usually referring to the whole of the cosmos.
This idea was first thought to be proposed by Pythagoras, but was later popularized by hermeticism through the understanding of the principle of correspondence. The principle of correspondence which states; “That which is Below corresponds to that which is Above, and that which is Above corresponds to that which is Below, to accomplish the miracle of the One Thing.” This understanding presents the idea that there is a similarity of pattern, nature, or structure between smaller, and larger aspects of existence. This understanding was originally applied to the connection between humans, and the universe, and was also a foundation for some forms of panpsychism.