The notochord is a flexible, rod-shaped structure found in the embryos of all chordates, which are a group of animals that includes fish, amphibians, reptiles, birds, and mammals, including humans. It is located along the dorsal (back) side of the developing embryo and serves as the primary structural support for the body. The notochord also plays an important role in the development of the nervous system, as it induces the formation of the neural tube, which gives rise to the brain and spinal cord. In some species, such as fish, the notochord persists throughout life, while in others, including humans, it is replaced by the vertebral column during development.