During my PhD, we discovered that and how archaea - as a rare and neglected part of the gut microbiota - could indeed impact and interact with the human immune system. Since then I am fascinated by the complex molecular crosstalk between our microbial diversity and us – with a special focus on the microbes. Understanding how human-associated microbes evolve themselves (and us) over time might be the key to unravel their role in the development of chronic diseases.