The second hermetic principle is the law of correspondence
“As above, so below; as below so above."
This principle means that for every event that occurs in our natural world it is either a microcosm or a macrocosm of something else. For example, our blood running through our veins is a microcosm for rivers flowing in and out of larger bodies of water. Another great example is hen bacteria interact with other bacteria they often exchange genetic material, this allows both bacteria to evolve and become more fit for their environment. This is similar to humans, when we interact with other humans, we exchange thoughts and ideas, and come away from the experience more fit for future encounters. This is akin to communities that encounter other communities, meeting to exchange goods or services that strengthen both communities.

So What?

The idea of microcosm to macrocosm means that if we can understand ourselves we can understand the universe. Everything to be learned is already within us as a macrocosm. Throughout all levels of existence there are definite interactions and patterns that repeat themselves. Knowledge of these patterns is the key to being masters of this dimensional reality.