What Are the 6 States of Matter?

Most people learn about three states of matter in school, but physicists recognize at least six distinct forms that matter can take: solid, liquid, gas, plasma, Bose-Einstein condensate, and fermionic condensate. The first three are part of everyday life, plasma makes up most of the visible universe, and the final two exist only under extreme laboratory conditions near absolute zero. What separates one state from another comes down to how particles are arranged and how much energy they carry, and once you push past ordinary temperatures in either direction, matter starts doing things that seem to defy common sense.

Solids, Liquids, and Gases

The three classical states are the ones you can observe without any special equipment. In a solid, particles are packed tightly together and held in place by strong attractive forces between them. They vibrate around fixed positions but don’t wander. This is why solids hold their shape. In a liquid, particles have more energy and sit farther apart. They can slide past one another, which is why liquids flow and take the shape of their container, but intermolecular forces still keep them loosely bound together. In a gas, particles have enough energy to break free of those forces entirely. They spread out to fill whatever space is available and move quickly in all directions.

1Research Starter. Kinetic theory

Temperature and pressure govern which state you get. Add heat to ice and you get water; add more and you get steam. But the transitions between these three states are reversible and familiar. What makes the remaining three states interesting is that they require conditions far outside normal human experience, and the behavior of matter in those states can be genuinely strange.

Plasma

Plasma is sometimes called the fourth state of matter, and it is by far the most common state in the universe. Stars, including the Sun, are made of plasma. So are lightning bolts, neon signs, and the auroras that shimmer near the poles. Despite being everywhere in space, plasma is relatively rare on Earth’s surface under natural conditions, which is why it took longer for scientists to recognize it as a distinct state.

What makes plasma different from a gas is ionization. In a regular gas, atoms are electrically neutral: each one has the same number of electrons orbiting its nucleus as there are protons inside it. In plasma, atoms have been stripped of one or more electrons. The result is a soup of free-floating electrons and positively charged ions. Because these particles carry electrical charge, plasma responds to magnetic and electric fields in ways that ordinary gas does not. This is why plasma can be shaped and contained by magnetic fields, a property that researchers are trying to exploit in fusion energy reactors.

You don’t need exotic equipment to encounter plasma. A candle flame contains a thin layer of it. Fluorescent light bulbs work by running an electric current through a gas until it becomes plasma and emits light. Plasma televisions, now largely replaced by other technologies, lit up pixels using tiny cells of ionized gas. The transition from gas to plasma happens when you add enough energy to start knocking electrons loose, whether through extreme heat, strong electric fields, or intense radiation.

Bose-Einstein Condensates

If plasma is what you get when matter is extremely hot, Bose-Einstein condensates (BECs) are what you get when matter is extremely cold. Predicted theoretically by Satyendra Nath Bose and Albert Einstein in the 1920s, BECs were not produced in the laboratory until 1995. They form when a gas of certain types of atoms is cooled to temperatures within a tiny fraction of a degree above absolute zero, roughly negative 273 degrees Celsius.

At those temperatures, something remarkable happens. Individual atoms lose their separate identities. Instead of behaving as distinct particles bouncing around independently, they all drop into the same quantum state and begin acting as a single entity. If you could watch the process, you would see a cloud of atoms that were moving around independently suddenly collapse into a single, nearly motionless blob. The atoms are no longer meaningfully separate. They behave collectively, almost like one giant “super-atom.”

Creating a BEC traditionally requires an elaborate cooling process. Researchers typically use lasers to slow atoms down, then evaporate the hottest remaining atoms away, leaving only the coldest behind. This evaporative cooling step has long been considered essential. But in 2024, researchers demonstrated that a small BEC of roughly 250 rubidium-87 atoms could form inside a microscopic optical trap using only polarization gradient laser cooling, without any evaporative step at all, and in as little as 40 milliseconds.

2PubMed. Bose-Einstein Condensation by Polarization Gradient Laser Cooling

That result challenges what had been a longstanding consensus in the field and could eventually simplify BEC production. For now, BECs remain confined to specialized physics labs, but the techniques for making them keep getting more accessible.

Fermionic Condensates

Fermionic condensates are the sixth commonly listed state of matter, and they are closely related to BECs but built from a fundamentally different class of particle. To understand why they are treated as a separate state, you need to know that all particles in nature fall into one of two categories. Bosons are particles that can pile into the same quantum state with no restrictions; this is exactly what happens in a BEC. Fermions, on the other hand, obey a strict rule: no two identical fermions can occupy the same quantum state at the same time. Electrons, protons, and neutrons are all fermions.

Because of this exclusion rule, fermions cannot simply collapse into a shared state the way bosons do. Instead, at extremely low temperatures, fermions form pairs. These pairs, called Cooper pairs after physicist Leon Cooper, behave as composite bosons and can then condense collectively. The first fermionic condensate was created in 2003 by cooling potassium-40 atoms to near absolute zero and using magnetic fields to coax them into pairing up.

Fermionic condensation is closely related to superconductivity, the phenomenon in which certain materials conduct electricity with zero resistance when cooled below a critical temperature. In a superconductor, electrons form Cooper pairs that move through the material without scattering. Modern theoretical work continues to refine how researchers identify and characterize these paired condensates, including frameworks that can detect both conventional and exotic forms of superconducting order by analyzing the internal structure of particle pairs.

3arXiv. Cooper Condensation and Pair Wave Functions in Strongly Correlated Electrons

The practical stakes are significant. If researchers can fully understand fermionic condensation, it could help unlock room-temperature superconductivity, a goal that would revolutionize power transmission, computing, and transportation. That goal remains distant, but fermionic condensates provide one of the clearest windows into the physics that would make it possible.

Why Some Lists Have More Than Six

Six is a convenient number for introductory purposes, but it understates how many distinct states of matter physicists have identified or proposed. The number depends on who is counting and how broadly you define “state.” Several additional forms of matter exist under conditions so extreme that they only occur in nature inside dying stars or particle accelerators.

Degenerate matter is one example. When a star runs out of fuel and collapses, the remaining material gets crushed to extraordinary densities. In a white dwarf, the remnant of a star roughly the mass of the Sun, electrons are packed so tightly that quantum mechanical effects prevent them from being squeezed any further. This electron degeneracy pressure is what keeps the star from collapsing entirely. In a neutron star, the crushing goes further: protons and electrons merge into neutrons, and neutron degeneracy pressure takes over as the stabilizing force.

4Research & Development in Material Science. Electron and Neutron Degeneracy on Stellar Life Cycle

Even more extreme is quark matter, sometimes called quark-gluon plasma. Under normal conditions, quarks are permanently confined inside protons and neutrons. But at fantastically high temperatures or densities, quarks can break free and roam independently. This state is thought to have existed in the first microseconds after the Big Bang, and physicists have briefly recreated it in particle colliders. Some researchers have investigated whether strange quark matter, which includes a type of quark not found in ordinary protons and neutrons, could exist in the cores of the heaviest neutron stars. Studies of a neutron star measured at about twice the mass of the Sun have explored whether its core might contain either strange quarks in a confined state or fully deconfined quark matter.

5Acta Physica Polonica B Supplementum. Strangeness in the cores of neutron stars

Then there are time crystals, first proposed in 2012 and experimentally realized a few years later. A time crystal is a system of particles that repeats its configuration not in space, like the atoms in a regular crystal lattice, but in time. The particles oscillate between states in a pattern that repeats indefinitely without absorbing or releasing energy. Whether time crystals should count as a “state of matter” or as a distinct phase within an existing state is still debated, but they have become a serious topic in quantum physics research.

Superfluid and supersolid states further complicate the count. Superfluids flow with zero viscosity, meaning they can creep up the walls of a container and escape, and they never lose kinetic energy to friction. Supersolids combine the rigid lattice structure of a solid with the frictionless flow of a superfluid. Both have been observed in laboratory settings at ultra-low temperatures. Some physicists classify these as phases within BEC physics rather than entirely separate states, which is one reason the official count varies.

What Bose-Einstein Condensates Are Actually Used For

BECs sound like pure curiosities, but they have turned into serious tools for precision measurement. Because all the atoms in a BEC share a single quantum state, the condensate behaves like a coherent matter wave, analogous to how laser light is a coherent light wave. That property makes BECs extremely sensitive to tiny forces and accelerations, which is useful for building instruments called atom interferometers.

An atom interferometer works by splitting a matter wave, sending the two halves along different paths, and then recombining them. Any force that acts differently on the two paths shows up as a shift in the resulting interference pattern. Researchers have already taken this technology into space. An experiment aboard a sounding rocket used BECs to perform atom interferometry in microgravity, demonstrating interference patterns that could be used for ultra-precise measurements of gravity and for testing whether all forms of matter fall at the same rate, a central prediction of general relativity.

6Nature Communications. Ultracold atom interferometry in space

Ground-based applications are progressing as well. A technique called twin-lattice atom interferometry can impart very large momentum kicks to BEC atoms, vastly increasing the sensitivity of the instrument. This approach has been proposed for building enhanced gyroscopes, gravity-gradient sensors, and even terrestrial detectors for very-low-frequency gravitational waves, the kind produced by merging supermassive black holes that current detectors cannot pick up.

7PubMed Central. Twin-lattice atom interferometry

These are not distant theoretical proposals. Working prototypes exist, and several space missions have been designed or proposed around BEC-based instruments. The transition from laboratory curiosity to practical sensor technology is well underway.

How Phase Boundaries Get Blurry

One thing that surprises people learning about states of matter is that the boundaries between them are not always clean. The familiar example is glass. Despite feeling unmistakably solid, glass does not have the orderly crystal lattice that defines a textbook solid. Its atoms are arranged more like a liquid that has been frozen in place. Whether glass is a “true” solid, an extremely slow-moving liquid (a popular myth), or something else entirely has been a surprisingly contentious question in physics for decades. The current consensus treats glass as an amorphous solid, a solid without long-range atomic order, but the theoretical understanding of how and why the glass transition happens remains an active area of research.

Supercritical fluids present another case where boundaries dissolve. Above a specific temperature and pressure, known as the critical point, the distinction between liquid and gas ceases to exist. A supercritical fluid can dissolve substances like a liquid but diffuse through materials like a gas. Supercritical carbon dioxide is used commercially as a solvent in processes like decaffeinating coffee and dry cleaning, precisely because it straddles the line between two states.

Liquid crystals are yet another boundary case. The screens on most phones and monitors use materials that flow like liquids but have molecules arranged in orderly patterns like crystals. They sit in a state between solid and liquid, and their optical properties change when you apply an electric field, which is how individual pixels get turned on and off.

These in-between cases are a reminder that the six-state list, while useful, is a simplification. Matter does not always cooperate with neat categories. The deeper physicists look, the more ways they find for particles to organize themselves, and each new arrangement can behave differently enough to earn its own label.

Quantum Correlations in Condensed States

One of the more surprising aspects of exotic states like BECs and fermionic condensates is that the quantum effects they exhibit are not limited to tiny clouds of atoms in a lab. Similar quantum correlations show up in ordinary condensed matter, the solid materials that make up everything from magnets to semiconductors. Researchers can detect entanglement and other quantum effects in bulk materials using collective measurements, including magnetic susceptibility and spectroscopic techniques that probe how particles within a material are correlated with one another.

8Advanced Quantum Technologies. Witnessing Entanglement and Quantum Correlations in Condensed Matter: A Review

This means that the exotic quantum behavior associated with the fifth and sixth states of matter is not entirely alien to everyday materials. The difference is one of degree and clarity. In a BEC, quantum coherence is total and unmistakable: every atom is in lockstep. In a chunk of magnetic iron at room temperature, quantum correlations between electron spins still exist and still influence the material’s properties, but they are partial, noisy, and tangled up with thermal fluctuations. The exotic states strip away that noise and let researchers study quantum behavior in its purest form, which is part of why they remain so scientifically valuable even when they have no obvious commercial application on their own.