If you want to live to a grand old age, it might help to think of yourself not as a human, but rather a holobiont – a collective of human cells plus the trillions of microbes that live in and on you.

I F YOU DREAM of affording a place to yourself, what town you live in is as important as what you earn. Across American cities average rents vary more than average wages do. Now in its third year, our ...