Wormlike micellar fluids are fluids that has very long (or wormlike) micelle rods suspended in the fluid. Micelles are groupings of molecules with a polar and nonpolar region. When introduced to a fluid the individual molecules will initially dissolve. However, as concentrations increase they will form structures as the polar regions will either be attracted to the fluid or repulsed by it. Thus they also self heal when ripped apart. In wormlike micellar fluids, these micelles form long rod shapes that give the fluid viscoelastic and birefractive properties. For more information on birefractive properties see the post.