Testisler, or testes, are the male reproductive organs responsible for producing sperm and hormones, primarily testosterone. They are typically oval-shaped and located in the scrotum, which helps regulate their temperature for optimal sperm production. In humans and many other animals, the testisler develop during puberty, leading to increased hormone levels and the maturation of sperm. Each testis contains seminiferous tubules, where sperm cells are formed, and interstitial cells, which produce testosterone. Proper functioning of the testisler is essential for male fertility and overall reproductive health.