Until recently, we had thought our microbes hardly mattered, but science is revealing a different story, one in which microbes run our bodies; remaining a healthy human is impossible without them.

In this riveting, shocking, and beautifully written book, biologist Alanna Collen draws on the latest scientific research to show how our personal colony of microbes influences our weight, immune system, mental health, and even our choice of partner. She argues that so many of our modern diseases—obesity, autism, mental illness, digestive disorders, allergies, autoimmune afflictions, and even cancer—have their root in our failure to cherish our most fundamental and enduring relationship: that with our individual colony of microbes.