A vortex is a region in which a fluid or gas flows in a spiral toward the vortex center. The speed of fluid flow is fastest at the center of the vortex, and decreases with distance from the vortex center. Tornados and whirlpools are examples of vortices. Quantized vortices will appear in a superfluid when it is rotated fast enough, and quantized vortices will form in the electron gas inside a type-II superconductor when it is placed in a strong enough magnetic field.