The boundary layer is a very thin layer of air flowing over the surface of an object (like a wing). As air moves past the wing, the molecules right next to the wing stick to the surface. Each layer of molecules in the boundary layer moves faster than the layer closer to the surface. The greater the distance (n) from the surface, the greater the velocity (V) of the molecules. At the outer edge of the boundary layer, the molecules move at the same velocity (free stream velocity) as the molecules outside the boundary layer. Ludwig Prandtl revolutionized fluid dynamics when he introduced the boundary layer concept in the early 1900s.