Your microbiome refers to the collection of microscopic organisms that live within your body and on the surface of your skin. We co-exist with these microscopic beings in a state of symbiosis, or living together in harmony. The interactions between our microbiome and our state of being are complicated and delicate, and much has yet to be discovered.

These interactions are so important that we cannot understand the lives of the creatures around us without understanding how microbiota aid in their lives. In the same vein, we cannot truly understand microbiome interactions without the knowledge of how other species interact with their microbiota. The link between bacteria and ourselves can offer vast amounts of knowledge about the world around us.

We are never truly alone, as our microbiome always accompanies us. There are layers and layers of mystery, interaction, and tiny ecosystems carried around in our bodies. Walt Whitman puts this into perspective: “I contain multitudes” (5).

To understand our microbiome, we must go back and look through the history of Earth. Yong asks the reader to look at the planet’s history as a one-year span. In this analogy, it is December 31st, and humans have only existed for a total of 30 seconds in that entire year.