Glass-ceramics combine the properties of glasses with the benefits of conventional sintered ceramics.
Most commonly they are manufactured in a process in which a pre-manufactured glass is subjected to a specific heat treatment. This treatment results in a controlled nucleation and crystallisation of the glass. The glass partially crystallises, and the glass-ceramic develops a structure comprising an amorphous (glassy) phase and at least one embedded crystalline phase .
Glass-ceramics can range from highly crystalline to containing a more substantial glassy phase. As they contain crystalline phases and, therefore, also grain boundaries, glass-ceramics can range from transparent to opaque [1,2].
Depending on the microstructure and the chemical composition of glass-ceramics, their properties can be tuned to meet demanding requirements. In general, glass-ceramics exhibit almost zero thermal expansion and high toughness. In addition, they are resistant to thermal shock and have a high impact resistance .
Glass-ceramics can be subdivided into two categories: oxide an non-oxide. Oxide glass-ceramics include silicate (SiO2), borate (B2O3), phosphate (P2O5) and germinate (GeO2) type materials. Non-oxide glass-ceramics include chalcogenide, halide and metallic type. 
With their thermal and mechanical characteristics, glass-ceramics are highly advantageous for use as cooktops and are present in most modern kitchens. They are also used for smartphone screens, in biomedical engineering and in advanced optics, for example for thermal shock resistant colour filters.
If you would like to know more about glass ceramics, read this article: "Glass-ceramic for extreme conditions".
 W. Höland, G. H. Beall, Glass Ceramic Technology. John Wiley & Sons, 2012.
 B. Karmakar, Functional Glasses and Glass-Ceramics: Processing, Properties and Applications. Butterworth-Heinemann, 2017.
Glass-ceramic is a material that combines two types of materials to form a product that is in a class of its own between glasses and polycrystalline ceramics.