The trillions of microbes in the human body, including pathogenic and symbiotic microbes, as well as their genes, proteins, and metabolites, make up the human microbiome. Importantly, an imbalance of pathogenic microbes has the potential to lead to serious illness and disease. But in a healthy person, the symbiotic microbes can regulate the environment to prevent the pathogenic microbes from proliferating. Sometimes, when the balance of the microbiota is upset, the number of symbiotic microbes falls while the pathogenic microbes have more room to grow and develop. These conditions can lead to the development of disease and illness. Researchers are currently looking into the relationship between certain microbes and health and disease.