This hour, we dive into the messy mystery in the middle of us. What's going on down there? And what can the rumblings deep in our bellies tell us about ourselves?  We join author Mary Roach and reach inside a live cow's stomach. Talk with writer Frederick Kaufman about our first peek into the wonderful world of human digestion that came about thanks to a hunting accident. And explore with show regular, science writer, and fellow water drinker, Carl Zimmer, about the trillions of microscopic creatures that keep us regulated, physically, but also, maybe, emotionally and spiritually. Our newsletter comes out every Wednesday. It includes short essays, recommendations, and details about other ways to interact with the show. Sign up (https://radiolab.org/newsletter)!Radiolab is supported by listeners like you. Support Radiolab by becoming a member of The Lab (https://members.radiolab.org/) today.Follow our show on Instagram, Twitter and Facebook @radiolab, and share your thoughts with us by emailing radiolab@wnyc.org. Leadership support for Radiolab’s science programming is provided by the Gordon and Betty Moore Foundation, Science Sandbox, a Simons Foundation Initiative, and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.