Have frequent, burning pee? Cramping or the urge to pee even though you just went? If you haven't yet, you probably will eventually—along with an estimated 60% of women and 10% of men. That's the large slice of the population that experiences a urinary tract infections (UTI) at least once. Many people avoid talking about these infections, but about one in four women experience recurring UTIs. No matter what they do, the infections come back, again and again. So today on the show, Regina G. Barber takes producer Rachel Carlson on a tour of the urinary tract. We zoom into what recurring UTIs may have to do with changes on the DNA of our bladder cells and the hidden bacterial houses in our bladder walls. Read more about the latest research into recurring UTIs in this article from our colleagues at NPR's global health blog, Goats and Soda.Got questions about the big and small of our universe? Email us at shortwave@npr.org.