An amphiphilic compound such as a surfactant molecule is a very simple molecule. Yet, when dissolved in water, it spontaneously self-assembles into a multitude of micellar structures such as globules, rods, disks, and vesicles. Even in dilute solutions containing only about 1 % of surfactant, these primary structures can organize themselves on a macroscopic scale so that the whole system in a test tube can be completely ordered. Such systems can have very remarkable macroscopic properties, for example, a yield stress, complex fluid behavior, or iridescence under illumination.
The shape of the micellar structures is always determined by the area a that a surfactant molecule occupies at a micellar or bulk interphase. This area can be controlled or tuned by the mixing ratio X between surfactants or between surfactants and cosurfactants. The different assemblies which then result with the variation of X are discussed, together with the macroscopic properties of the systems and some applications where these properties are of use.