How do scientists describe the independent microorganisms (comprised of about 90% of our 100 trillion cells) in the human body?

According to a recent National Institutes of Health (NIH) estimate, 90% of cells in the human body are bacterial, fungal or other non-humans. Many scientists concluded that bacteria enjoy a commensal relationship with their human hosts. Microbes not only live outside the human but live equivalently inside the human body that keeps him healthy.

Scientists called human skin a "virtual zoo of bacteria". Some scientists compared the diversity in the human gut to a rain forest. The human gut alone contains on average 40,000 bacterial species.

According to the Human Microbiome Project in 2007, dozens of research teams have gathered data that redefine what it means to be human. Some commentators have gone so far as to refer to the human body as a superorganism whose "whose metabolism represents a combination of microbial and human attributes.