Milk is more than just a food for babies. Breast milk has evolved to deliver thousands of diverse molecules including growth factors, hormones and antibodies, as well as microbes. Elizabeth Johnson, a molecular nutritionist at Cornell University, studies the effects of infants’ diet on the gut microbiome. These studies could hold clues to hard questions in public health for children and adults alike. In this episode of “The Joy of Why” podcast, co-host Steven Strogatz interviews Johnson about the microbial components that make breast milk one of the most wondrous biofluids found in nature. You can read the transcript for this episode and see the image of the micrograph Johnson references on our website.