On a sunny Friday morning in Venice, Valerie Rosas is standing in a kitchen, carefully cutting little pieces of meat with a chef's knife on a disposable cutting board. But it's not lamb filet or beef brisket she's preparing. It's human placenta. Rosas is a placenta encapsulationist — which means she helps transform the organ expelled after childbirth into something edible: Depending on her client's preference, it might be ready-to-pop pills, smoothie packs or salves. Eating the vitamin-rich placenta is touted as a way for new mothers to increase milk supply, boost energy and iron levels, level out hormonal fluctuations...