And testes are very two important roles. Firstly, they play a role as a reproductive organ. So that means they produce specialized types of cells known as sperm cells that are involved in our human reproduction cycle. And secondly, testes also play a role as an endocrine gland and that means they are capable, capable of releasing and producing specialized hormones that are required by our body. Now, in this lecture we're going to focus on the latter. We're going to focus on the endocrine capability of testes.