The human body is home to trillions of microorganisms, most of which live in the digestive system. Collectively kn as t microbiome, th tiny orga play a vi role i digestion a immunity. Scien have disco that t composition o the micro varies consid from per to per. Diet, medic and ev early chil experiences c influence i. Researchers are now investigating whether changes to the microbiome could help treat certain diseases.