Aizawa attractor
The Aizawa attractor is a chaotic flow that winds around a sphere-like shell and threads a narrow tube along its axis.
Equations
Read the first two equations in polar form and they say something simple: the point turns around the z axis at a constant rate d, and its distance from the axis grows while z is above b and shrinks while it is below. The third equation decides the height. The small fzx3 term is the only thing that breaks the symmetry around the axis.
History
The system is usually attributed to Yoji Aizawa. It has become a favourite of generative artists, because its depth only shows once you turn it: the shell and the tube through it read as a flat smudge from most fixed angles.
What to look for
Follow the red head up the central tube. It spills over the top, slides down the outside of the shell, and is drawn back into the tube near the bottom. Turn the attractor to look down the tube.