Overview of development of microbiota. The gastrointestinal tract (GI) is most sterile during the in utero stage. The first colonization happens based on mode of delivery either C-section or natural (vaginal delivery). Corynebacterium sp. is thought to be early colonizers in C-section and Lactobacillus sp. in the vaginal delivery. As the time progress the commensal bacterial community grows and is influenced by the solid food intake. During the initial stages of microbiota establishment the TLR receptor actions are minimal allowing growth of commensals. Eventually the immune system also grows by demarking the commensals and pathogens. Bacteroidetes domination begins after two years of birth. The relative stability is attained at the adulthood with Bacteroidetes and Firmicutes dominating. The alteration happens with use of antibiotics, obesity, GI orders, and diet. During elderly the relative stability declines, commensal community reduces, and pathogenic species like Clostridium increases. Malnutrition, alcohol abuse, decline in metabolism, frequent hospitalization, nosocomial infections (Clostridium difficile), and other pathogenic infections leading to Polypharmacy and ultimately to various inflammatory diseases.