Envision, a tumor so loathsome that it violates the very laws of physiology, rendering normal tissues at odds with their own nature. According to Merriam Webster, a teratoma is defined as a tumor derived from more than one embryonic layer and consisting of a heterogeneous mixture of tissues, such as epithelium, bone, cartilage, or muscle. The name teratoma comes from the ancient Greek prefix terato, meaning monster, combined with the suffix oma, meaning mass. Therefore, the term teratoma can be interpreted as denoting a monstrous mass. Indeed, teratomas have a grotesque quality, in that they are not constrained by normal anatomical boundaries. Even more, they can even contain hair, teeth, fat, bones and sometimes complex organs (see fig. 1). The etiology of a teratoma is not yet fully understood, as it belongs to the category of germ cell tumors. However, teratomas are most commonly found in certain organs, such as the brain, thyroid, liver, lungs, ovaries and testes. Subsequently, teratomas are thought to be caused by the abnormal development or migration of germ cells or embryonic (stem) cells during embryogenesis. If the teratoma is of germinal origin, it will then be located either in the testicles or in the ovaries. However, if it originates from embryonic cells, then it can be located anywhere from the sutures of the skull to the coccyx. With this in mind, embryonal teratomas are congenital, meaning they either exist prenatally, at birth, or develop within a month of birth. Germ cell teratomas are not thought to be congenital, but this is not known for certain. Although most teratomas are benign because they are encapsulated, some can potentially be malignant. Additionally, a teratoma can be classified into two groups, mature and immature. A mature teratoma is usually benign and may be solid, cystic, or both (see Fig. 2). Mature teratomas are highly differentiated and contain all types of tissue. A specific type of mature teratoma that usually contains hair follicles inside, is known as a dermoid cyst and occurs primarily in the ovaries and in the sutures of the skull (see fig 3). An immature teratoma is a type of malignant germ cell. tumor, and may contain the same entities as a mature teratoma, with the exception of the primitive neuroepithelial, considered the "stem cells" of the nervous system.