Our bodies are home to several billions of bacteria, fungi, yeasts, viruses, and parasites grouped in ecosystems. The general term for them is microbiotas, and our overall equilibrium depends on their good health. Should even one of them be altered, that's more than enough for us to become more susceptible to everday ailments and diseases: stress, canker sores, gingivitis, urinary infections, fungal infections, colds, bloating… So, how do we maintain sustainable equilibrium among our microbiota?