This issue of MRS Bulletin focuses on the preparation and application of hybrid organic–inorganic materials, which are broadly defined as synthetic materials with organic and inorganic components. Hybrid organic–inorganic materials are of two kinds: homogeneous systems derived from monomers or miscible organic and inorganic components, and heterogeneous and phase-separated systems with domains ranging from angstroms to micrometers in size.

Hybrid materials lie at the interface of the organic and inorganic realms. These materials offer exceptional opportunities not only to combine important properties from both worlds, but also to create entirely new compositions with truly unique properties.

The possibility of combining the properties of organic and inorganic components in a unique composite material is an old challenge that dates to the beginning of the industrial era. Some of the earliest and most well-known organic–inorganic representatives are derived from the paint and polymer industries, where inorganic pigments or fillers are dispersed in organic components such as solvents, surfactants, and polymers to yield or improve optical and mechanical properties.

Nano-ordered composite materials consisting of organic polymers and inorganic compounds have been attracting attention for their use in creating high-performance or high-functionality polymeric materials. The term “polymer hybrid” describes blends of organic and inorganic components with molecular-level dispersions.

Reinforcement of polymers with a second phase, whether inorganic or organic, to produce a polymer composite is common in the production of modern plastics. Polymer nanocomposites (PNCs) represent a radical alternative to these conventional polymer composites.

Sol-gel processing readily yields both inorganic and hybrid organic–inorganic materials. Commercial applications of solgel technology preceded the formal recognition of this technology as an important field of study. Likewise, successful commercial hybrid organic–inorganic polymers have been part of manufacturing technology since the 1950s.