Your gut microbiome is made up of trillions of bacteria, fungi, protozoa, and viruses. It is unique to each person and is established very early in life; your parents health and genetics, how you were birthed, and whether you were breast or bottle-fed are early determinants of microbiome variation.
The microorganisms of the gut microbiome play a key role in food digestion and absorption, but also help to regulate your metabolism, weight, mood, and immune function. While it is initially determined at birth, your gut microbiome is constantly being shaped by many factors including stress, genetics, illness, and diet.