Eutectics are a paradigm of micron scale composite materials with improved properties. Improved mechanical properties and thermal stability of eutectics as compared with ceramics or single crystals of component phases are a consequence of the presence of huge amounts of interfaces. Interface morphology and ordered structures also invites to explore other properties of regular eutectics such as light guiding effects, anisotropic ion conduction, use as structured substrates for patterned films, etc. In this work we report on the production of several eutectic crystals of wide band gap materials, grown from the melt by unidirectional solidification. The structure, mechanical properties and interface morphology were determined using different techniques including X-ray diffraction, SEM, TEM, Raman and optical spectroscopy techniques. Examples of lamellar microstructures are provided by the ZrO2-CaO, ZrO2-NiO and CaF2-LiF systems. Planar light guiding and anisotropic ion conduction are some of the unconventional properties of these regular composites. ZrO2-MgO, ZrO2-Al2O3 and CaF2-MgO are examples of fibrous eutectics. The alumina-zirconia composite presents excellent mechanical properties also related to the presence of residual thermostresses that have been measured using different piezospectroscopic effects. The fluorite-magnesia eutectic is an example of semifaceted non-regular composite showing light guiding effects.