The differentiation of totipotent stem cells is like a highway that is constantly extending and differentiating. With the advancement of technology, it is possible to genetically program mature cells to become embryonic stem cells that can differentiate in all directions. iPS is very mysterious until one sees it in the laboratory. Inducing cells carrying disease-causing genes into iPS and then conducting scientific research is a very good experimental model. Colleagues in the lab proved the reliability of the model by beating iPS into animals, which grew teratomas in just a few days. Mammals gradually differentiate from the trichoblast during the embryonic period and finally form an organism. If after the formation of the mature organism, there is still a differentiation of residual stem cells, it is possible to grow into a tumor, and if there are three germ layers of tissue, this is a teratoma. If it grows in the skull, it forms an intracranial parasite. A few years ago, a patient in his 20s had a tumor growing behind the three intracranial ventricles, and the pathology was teratoma. Later, obstructive hydrocephalus occurred in the emergency room, and a ventriculoperitoneal shunt was performed after ventriculoperineal puncture, and he walked through the ghost gate, and later received radiotherapy. Teratomas are associated with embryogenesis, and embryos differentiate on the midline as the longitudinal axis, so they tend to grow in midline locations, such as the saddle area, the three ventricles, the posterior part of the three ventricles, and in the spinal cord, mostly in the conus. The age of predilection is of course common in children, because as the child grows, so does the tumor, and after the age of 20 or so the growth of the organism ceases, and teratomas are less common at that time. There is no big difference in gender, and there is no big difference in the incidence of boys and girls. Surgery is the treatment of choice for intracranial teratomas, where the tumor is surgically removed and the next step in treatment is decided based on pathological findings. Teratomas are formed by the differentiation of residual tissues. As long as there is differentiation there will be cell growth and tumor activity, which is why malignant teratomas exist. These tumor cells are very actively differentiated and require postoperative radiation therapy to kill the residual cells. Encountering iPS thought of teratoma, in neurosurgery they are called intracranial parasites, and isn’t the neurosurgeon the scavenger of the brain.