The metanephros is the final and most advanced stage of kidney development in vertebrates, including humans. It forms during the embryonic stage and is responsible for the production of urine and the regulation of water and electrolytes in the body. The metanephros develops from the mesoderm and is essential for maintaining homeostasis. In humans, the metanephros begins to function around the 10th week of gestation, taking over the roles of earlier kidney structures, the pronephros and mesonephros. This organ continues to develop and mature throughout fetal life, ultimately becoming the permanent kidney that will function after birth.