Some young mothers, when bathing their babies, may inadvertently find that they cannot feel or can only feel one testicle in their child’s scrotum. Mothers often break out in a cold sweat and are at a loss for words, which is called cryptorchidism. As the name suggests, cryptorchidism is a deformed state in which the testicles do not descend into the scrotum, either bilaterally or unilaterally, after the child is born. The main reason why the testicles must descend into the scrotum is to ensure the normal development of the testicles. If the testicles in cryptorchidism do not descend into the scrotum in time, then the development of the testicles will be seriously affected and the function of the testicles to produce sperm and secrete androgens will be impaired. Cryptorchidism puts the testes under relatively high temperature, so that the testes cannot produce sperm normally. In bilateral cryptorchidism, infertility can be caused by azoospermia, and only 33% of patients can have children; in unilateral cryptorchidism, the opposite testicle can be affected, and only 87% of patients can have children. The chance of tumor in cryptorchidism is 40 times higher than that of normal people. This is another major reason why cryptorchidism must undergo testicular descent fixation surgery. In addition, patients with cryptorchidism have up to a 90% chance of having a combined inguinal hernia on the affected side, and there is an increased chance of testicular torsion in cryptorchidism. The treatment of cryptorchidism can be divided into two parts: medication and surgical treatment. The lower the location of cryptorchidism, the higher the success rate of drug treatment. The high cryptorchidism that cannot be felt can rarely be decreased by hormone treatment. Generally speaking, the success rate of drug treatment is about 20%. Surgery is the gold standard of cryptorchidism treatment, with a success rate of 70-90%. High cryptorchidism (such as intra-abdominal cryptorchidism) can be operated in two stages to make it descend gradually if it is difficult to descend. For children with intra-abdominal cryptorchidism over 10 years old, orchiectomy is recommended because of the high chance of malignant transformation. If the testicle does not descend within 1 year after birth, the possibility of self-descension is slim, so it is recommended that the operation should be completed before 12 to 18 months after birth. Hormonal medication given before or after surgery can be helpful for future fertility.