 What is the human microbiome? Though we don't often think about it, we're actually more non-human than human. Trillions of microscopic organisms or microbes call the human body home. Organisms such as bacteria, viruses, fungi and even microscopic animals live all over our body on our skin and even inside us. These tiny organisms make up our microbiota and most of them, about 95%, live in our gastrointestinal tract, more commonly known as our gut. And the combination of microbes, their genes, the environment they live in and the stuff they produce is called the human microbiome.