Mesocrystals: a new class of solid materials.

Possible types of, and formation mechanisms for, mesocrystals are summarized. Mesocrystals are a new class of solid materials, which can be regarded as assemblies of crystallographically oriented nanocrystals. Mesocrystals have high crystallinity as well as high porosity, making them promising substitutes for single-crystalline and/or porous polycrystalline materials in many applications such as catalysis, sensing, and solar-energy conversion.