Matter is anything that has mass and takes up space. Those two traits, mass and volume, are the defining characteristics that separate matter from massless phenomena like light or sound waves. Every object you can touch, breathe, or stand on is made of matter, and so are things you can’t see, like the air around you and the plasma inside stars.
What Matter Is Made Of
At the deepest level, all ordinary matter is built from just three types of particles: up quarks, down quarks, and electrons. Up and down quarks combine in groups of three to form protons and neutrons, which cluster together in an atom’s nucleus. Electrons orbit that nucleus, and the arrangement of these particles determines which element you get, from hydrogen to uranium and beyond. Every atom on the periodic table is assembled from these same three building blocks.
This framework comes from the Standard Model of particle physics, which describes how quarks and a broader family of particles called leptons (electrons being the most familiar) interact through fundamental forces. Despite the enormous variety of substances in the world, the recipe at the bottom is remarkably simple.
Mass, Weight, and Why They’re Different
Mass measures how much matter an object contains. It stays the same no matter where you are. Your mass on the Moon is identical to your mass on Earth. Weight, on the other hand, is the force that gravity exerts on that mass, so it changes depending on the strength of gravity around you. On the Moon, where gravity is about one-sixth as strong as Earth’s, you’d weigh roughly one-sixth as much, even though your mass hasn’t changed at all.
Mass is measured in grams or kilograms using a balance. Weight is measured in newtons (or pounds in everyday life) using a spring scale. The distinction matters in physics because mass is a fixed property of an object, while weight is always relative to the gravitational environment.
The Four Common States of Matter
Matter behaves differently depending on how much energy its particles have and how strongly they’re bound together. These behaviors fall into distinct phases.
Solids hold a fixed shape and a fixed volume. Their molecules are tightly bound by strong forces, which is why a rock doesn’t flow or expand to fill a container.
Liquids have a fixed volume but no fixed shape. The forces between molecules are weaker than in a solid, so a liquid flows and takes the shape of whatever container holds it. In the absence of gravity, a free-floating liquid pulls itself into a sphere.
Gases have neither a fixed shape nor a fixed volume. Molecular forces are very weak, so a gas expands to fill whatever space is available. Open a bottle of perfume in a room and its vapor will eventually reach every corner.
Plasma forms when matter is heated to extreme temperatures, like those on the surface of the Sun or during a spacecraft’s reentry into Earth’s atmosphere. At that point atoms themselves start breaking apart: electrons are stripped away from nuclei, leaving behind a mix of free electrons and charged ions. Because it contains charged particles, plasma responds to electromagnetic forces in ways that ordinary gases don’t. Despite being less familiar in daily life, plasma is actually the most common state of matter in the universe. Stars, lightning bolts, and neon signs all contain plasma.
Exotic States at Extreme Conditions
Beyond the four everyday phases, physicists have created and observed more unusual states. The best known is the Bose-Einstein condensate, first produced in a lab in 1995. Researchers cooled about 2,000 atoms to roughly 170 billionths of a degree above absolute zero using specialized laser and evaporative cooling techniques. At that temperature, a large fraction of the atoms collapse into the same quantum state, behaving as a single entity rather than individual particles. It’s essentially the opposite extreme from plasma: instead of atoms flying apart at incredible heat, they merge their identities at incredible cold.
Properties of Matter
Physicists and chemists describe matter using two categories of properties. Extensive properties depend on how much matter you have. Mass and volume are the clearest examples: a bigger sample has more mass and takes up more space. Intensive properties stay the same regardless of sample size. Density, color, temperature, and solubility are all intensive. A teaspoon of gold has the same density as a gold bar.
This distinction is useful because intensive properties help you identify a substance. If you measure an unknown metal’s density and find it matches the known density of aluminum, that’s a strong clue about what you’re holding. Extensive properties, by contrast, tell you how much of the substance you have, not what it is.
Matter and Energy
One of the most important ideas in modern physics is that matter and energy are deeply connected. Einstein’s equation E=mc² expresses this relationship: the energy contained in a piece of matter equals its mass multiplied by the speed of light squared. Because the speed of light is an enormous number (about 300 million meters per second), even a tiny amount of mass corresponds to a staggering amount of energy.
Einstein himself called this “the most important upshot of the special theory of relativity.” Before his work, mass in Newtonian physics could only change by physically adding or removing pieces of an object. Einstein showed that an object’s mass actually changes when it absorbs or emits energy. This principle is visible in nuclear reactions: when a particle of matter meets its antimatter counterpart, both are destroyed and their mass is converted entirely into energy. That process, called annihilation, is not just theoretical. It happens routinely inside particle accelerators and even in medical imaging technology.
Antimatter and Dark Matter
For every type of matter particle, there exists an antimatter partner with the opposite electrical charge. An electron carries a negative charge; its antimatter twin, the positron, carries a positive one. When a particle and its antiparticle collide, they annihilate each other and release energy. Antimatter is real and regularly produced in physics experiments, but it’s extremely rare in the natural universe. One of the biggest open questions in physics is why the universe contains so much more matter than antimatter.
Then there’s dark matter, which makes the picture even stranger. Ordinary matter, everything made of atoms, accounts for only about 5% of the total mass and energy in the universe. Dark matter makes up roughly 27%. The remaining 68% is dark energy, a mysterious force driving the universe’s accelerating expansion. Dark matter doesn’t emit, absorb, or reflect light, which is why it’s called “dark.” Scientists know it exists because its gravitational pull visibly affects how galaxies move and how light bends around massive cosmic structures, but no one has yet directly detected a dark matter particle. The matter you can see, touch, and measure is a small fraction of what’s actually out there.