Testicles must be below body temperature to produce normal sperm. Testicles are first formed in the embryo. During the development of the embryo, the testes gradually begin to move down until the final position. Some babies need surgery if they have abnormal development and their testicles have not dropped to their proper position after birth. Without surgery, testicular cancer may occur. And it must be early. If you are over a certain age, men may lose their fertility because their testicles are too hot. Similarly, if men often wear tight underwear and their testicles are tightly wrapped in underwear, the temperature, like body temperature, will affect the quality and quantity of sperm, thus affecting reproductive capacity.

When the weather is hot, the testicles will droop. When the weather is cold, the testicles will shrink to a place close to the body. When approaching the climax of sexual intercourse, the testicles will also rise to the place close to the body because of muscle contraction.