Chāng (Chang) and Ēn (Eng) Bunker were conjoined twins in the nineteenth century in the United States, the first pair of conjoined twins whose condition was well documented in medical records. A conjoined twins is a rare condition in which two infants are born physically connected to each other. In their youth, the brothers earned money by putting themselves on display as curiosities and giving lectures and demonstrations about their condition. The Bunker brothers toured around the world, including the United States, Europe, Canada, and France, and allowed physicians to examine them. Due to the popularity of their exhibition and their origin from Siam (later called Thailand), they became known as the Siamese twins, a term that was used to describe conjoined twins in general until the twentieth century. During their travels and, later, with the autopsy they received, the Bunker brothers provided insight about the development of twins and conjoined twins.