How the 40 trillion microbes in and on us shape our lives

We have about 40 trillion microbes living in and on us. In other words: a lot of germs. Until recently, we thought they were the enemy. Now we know they keep us alive. They are, as science writer Ed Yong says, the unsung heroes of human existence. Yong wrote about the promise and limitations of our microbiome in his new book titled, “I Contain Multitudes: The Microbes Within Us and a Grander View of Life.”