The testes, also known as testicles or male gonads, are two small organs that are found inside the scrotum. They have two primary functions: producing sperm and producing hormones, particularly testosterone. Sperm are produced in the seminiferous tubules of the testes, and once they are produced, they pass into the epididymis, where they mature and are stored until ejaculation. Testosterone is an important hormone during male development and maturation for developing muscles, deepening the voice, and growing body hair. It is secreted by cells that lie between the seminiferous tubules, known as the Leydig cells. The testes also produce inhibin B and anti-Müllerian hormone from Sertoli cells, and insulin-like peptide 3 (INSL3) and estradiol from the Leydig cells. The temperature of the testicles needs to be cooler than the inside of the body for optimal sperm production and quality, which is why the scrotum is located outside of the body.