Undescended testes happen when the gonads migrate from inside the pelvis out into the testicular sacs. Sometimes they do not make it all the way from the inside into the sacs. Testes needs to be in the sacs for temperature regulation; they function best when they are less than body temperature. They can not migrate at all, or they can stop somewhere along the way in the inguinal canals. Kids with inguinal testes are told they have a “hernia” and the doctor will do a surgery to put the testes into the sacs. If the testes are left inside the body for too long, they can be harmed by getting overheated, and they may not produce sperm as well or at all.