Very regularly aligned composite structures made of the two phases of a eutectic can be fabricated by unidirectional solidification of eutectics from the melt. A recent innovation is the use of chemical reactions taking place at the eutectic interface to produce new aligned composite materials. An example of this can be seen in the Figure, an SEM micrograph of an Ni/NiO interface showing long forks of Ni in an oriented NiO-ZrO2(CaO) eutectic.