In January 2017, Fiona the baby hippo was born at the Cincinnati Zoo six weeks premature and some 30 pounds underweight. Getting Fiona to put on pounds was a life-or-death matter. Unfortunately, nursing wasn’t an option, and the only hippo formula recipe on file was old and out of date. To devise a new one, team Fiona turned to the scientists at the world’s largest exotic-milk repository at the Smithsonian’s National Zoo. But could they do it in time, and would Fiona drink it?