I moved from Moscow to Rome with my family and two bicycles in 1998, and spent a lot of that year- and the next - obsessed, I am sorry to admit, with the bicycles. Italy, after all, was a place where thousands of middle-aged men felt perfectly comfortable spending many hours a week in brightly colored spandex.
We inherit every one of our genes, but we leave the womb without a single microbe. As we pass through our mother's birth canal, we begin to attract entire colonies of bacteria. By the time a child can crawl, he has been blanketed by an enormous, unseen cloud of microorganisms - a hundred trillion or more.