More than 10 times the number of microbes live in the human body than cells. And instead of responding with disgust and Purell, people are starting to see that not all microbes are bad. These microorganisms play an important part in our overall health, such as keeping the immune system in check and digesting food.
Emerging studies have also linked the microbe system in our intestines to things such as mental health, mood and human development.
So why the attitude change? A new wave of research suggests scientists can tinker with combinations of microbes to treat diseases, improve general health and even alter things like a person's complexion or the way they smell.
In perhaps the most successful example, doctors have used stool transplants to treat diarrhea-causing colitis. The microbe strains in fecal matter from a healthy donor can help repair the imbalance of bacteria in the patient's gut, curing an infection that has been resistant to antibiotics.
The attention to the human microbiome may be new, but its existence is not.
"It's the world of our many and myriad microbial companions that we've been carrying with us all along, going back through ancestral times," said professor David Relman, an infectious disease doctor at Stanford University and the VA Hospital in Palo Alto, California.
More recent discoveries are the results of years of research, kicked off by an influx of funding into the human microbiome by the National Institutes of Health
and the European Union.
Enterprising young companies are developing other products that tap the microbiome. Some, like uBiome, let you "sequence" your biome by mailing in a stool sample to see whether the bacteria in your gut put you in the same group as people who are vegetarians or who drink too much or who have schizophrenia.
Others claim they can alter your microbiome to improve health.
Some experts are wary that the benefits of microbiome research are being oversold.
"It's going to turn out to be complicated. I don't think there's going to be really easy fixes or solutions to (health) problems," Relman said. "But the general idea could be perfectly valid."
For example, the microbiome has been tied to obesity and diabetes, but Relman says microbes are just one of many factors, including genetics and lifestyle choices, that can lead to the diseases. A dietary supplement on its own is unlikely to cure diabetes, but if a person addressed the other issues and changed the makeup of their microbiome, that could have an impact.
Researchers are still unraveling the secrets of the human microboiome. Future microboiome treatments could be personalized and more precise, such as giving a patient a customized cocktail of microbe strains to treat diabetes.
Relman believes this new approach to treating illness is greatly preferable to our current overuse of antibiotics and disinfectants.
"I like the idea of taking an ecological approach to what is an ecological program and system, rather than the warfare approach," he said.