Did you know that microbes inhabit just about every part of your body? For the first time, a consortium of researchers organized by the National Institutes of Health has mapped the normal microbial make-up of healthy humans. They now calculate that there are more than 10,000 different microbial species and estimate between 81 and 99 percent of all microorganisms have been identified in generally healthy adults. They found that the human body contains trillions of microorganisms that outnumber human cells by 10 to 1. Because of their small size, these microorganisms make up only about 1 to 3 percent of the body's mass (e.g., if you weigh 100 pounds you have 1-3 pounds of microorganisms; if you weigh 200 pounds than 2-6 pounds of microorganisms, and so on). NHGRI's HMP program manager. "Microbes in the gut break down many of the proteins, fats, and carbohydrates into nutrients that you can then absorb; and produce beneficial compounds such as vitamins and anti-inflammatories. It appears that the distribution of microbial metabolic activities matters more than the species of microbes providing them (e.g., microbes can pinch hit for each other). The microbe composition changes when you get sick or take antibiotics.