The pia mater is the innermost layer of the meninges, a protective covering that surrounds the brain and spinal cord. It is a thin and transparent membrane that adheres closely to the surface of the brain and spinal cord, following their contours. The pia mater contains numerous blood vessels that supply nutrients and oxygen to the underlying nervous tissue. Its presence helps to cushion and protect delicate neural structures, contributing to their overall function and well-being.