Matter organizes into various phases or states of matter depending on its constituents and external factors like pressure and temperature. In common temperatures and pressures, atoms form the three classical states of matter: solid, liquid and gas. Complex molecules can also form various mesophases such as liquid crystals, which are intermediate between the liquid and solid phases. At high temperatures or strong electromagnetic fields atoms become ionized, forming plasma. At low temperatures, the electrons of solid materials can also organize into various electronic phases of matter, such as the superconducting state, which is characterized by vanishing resistivity. Magnetic states such as ferromagnetism and antiferromagnetism can also be regarded as phases of matter in which the electronic and nuclear spins organize into different patterns. Such states of matter are studied in condensed matter physics. In extreme conditions found in some stars and in the early universe, atoms break into their constituents and matter exists as some form of degenerate matter or quark matter. Such states of matter are studied in high-energy physics. In the 20th century, increased understanding of the properties of matter resulted in the identification of many states of matter. This list includes some notable examples.

Low-energy states of matter.

Classical states

Condensates, superfluids and superconductors

Magnetic states

Electronically ordered states

Topological states of matter

Classification by conductivity

Metallic and insulating states of materials can be considered as different quantum phases of matter connected by a metal-insulator transition. Materials can be classified by the structure of their Fermi surface and zero-temperature dc conductivity as follows:

Miscellaneous states

High energy states