Humans harbour a different microbiota depending on the tissue considered. Most of the microorganisms are contained in the gastro-intestinal tract (GIT) and this gut microbiota represents approximately 1014 cells that correspond to the highest bacterial density for any ecosystem. Our microbiota represents a huge diversity in term of species and functions. A healthy gut microbiota is composed of a well-balanced community of three permanent residents termed symbionts (with beneficial effects), commensals (no effect), and pathobionts (potentially induce pathologies under certain situations), but no pathogens. The term dysbiosis (microbial imbalance) has been related to many different kinds of pathologies although it is not clear whether the imbalance of such a microbiota is a cause or a consequence of the illness. Nowadays, the challenge of linking microbiota to human health and disease is being tackled by different research teams around the world with the aim to investigate the implication of potential beneficial bacteria that could be decreased in the studied microbiota of patients. From this perspective, it could be interesting to use them as potential probiotics to try to resolve dysbioses.