Who’s the barn boss? Just as importantly, who isn’t? Research is giving us a better understanding of equine hierarchies in both feral and domestic populations. And that insight is leading scientists to rethink the way we house, feed, and even work our horses. Respecting rank can improve our horses’ health and welfare as well as our own safety. By paying attention to hierarchy and giving our horses the opportunity to define it, we can help ensure harmony in the barn and beyond.