We’ve long been fascinated by the mysteries of reproduction. But that curiosity is piqued most intensely when something unexpected happens. The study of such “monstrous births,” as scientists once called them, propelled forward our understanding of how embryos and fetuses develop. And the key to unlocking this knowledge was found gathering dust in the basement of the Russian Academy of Sciences, in a macabre collection assembled by Czar Peter the Great. The story behind this collection reveals a little-known corner of the history of the life sciences and raises some big questions, like how do bodies we see as abnormal inform and define what we see as normal? And how does this influence how we think about disability today?