This Tool kit explores and catalogue part of our invisible organ: The microbiome. The microbiome is the collection of micro-organisms, such as bacteria, fungi, protozoa and viruses, that live in and on the human body. It consists of about 100 trillion microbes and outnumbers cells with human DNA by factor 10. The microbiome is therefore of greater complexity than the human genome itself. It is essential for the human body to function and plays a vital role for the immune system, nutrition and development of the body. The term holobiont describes the intimate and co-dependant relationship humans have with microbes. As it is becoming increasingly more difficult to think of the human as an individual, some have started to consider the human body as a mega-organism. Discoveries in the field of microbiology and medicine are a philosophical invitation to reflect on the idea of “self” and what should be considered human.