Most microbes that live, feed, and reproduce in your body are:

Your body is more than just you - it is an ecosystem for trillions of tiny microbes. These bacteria, viruses, and other single-celled organisms form communities inside and on your body. Together, these communities make up your microbiome. Your microbiome works with your body to keep your digestive system, immune system, and even your brain working properly. Your microbiome is so important to your survival, you could think of it as an extra organ.
Most microbes that live, feed, and reproduce in your body are:
bacteria
germs
fungi
Though some microbes in our bodies are germs that can make us sick, most work together to keep us alive and healthy. By far, most of these microbes are bacteria.
How many species of microbes live inside you?
about 100
about 1,000
as many as 10,000
Scientists think there may be about 10,000 different species of microbes living inside you! They're invisible to the eye, but they come in many different shapes and sizes.
There are more microbes in your body than human cells.
Seventy to ninety percent of all cells in the human body are microbial cells!
Your microbiome stays the same throughout your life.
Changing your diet can change which microbes live in your gut. Washing, antibiotics, hand sanitizers, and pets are just a few other things that affect your microbiome every day.
When you eat, you're feeding your microbes.
Microbes in your gut get their food from the food you eat. Some foods that feed helpful bacteria in your digestive system include beans, vegetables, fruits, and whole grains.
Definition: the collection of microbes on and in your body
Types: mostly bacteria; also viruses, fungi, and archaea
Functions: help with digestion, boost immune system, make vitamins, fight and prevent infections, affect our moods
Cool Fact: Microbes are so tiny, that billions can live in a drop of water.