Under usual, everyday conditions, carbon atoms exist as stacks of hexagonal sheets, but extreme pressure and heat rearrange them to form diamonds. Kateryna Kon/Science Photo Library via Getty ImagesCurious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.Can we remove or decrease spaces between atoms or molecules? – Paras, age 15, Uttarakhand, IndiaHave you ever seen a beautiful bunch of flowers packed tightly into a vase? A florist has to wiggle and arrange them perfectly so there are no empty holes.There are times when nature acts like a florist. Nature takes tiny building blocks called atoms and molecules and packs them together to fill up space. In gases, such as air, atoms and molecules are separated from each other by lots of space. In solids, such as a rock or a metal spoon, atoms are more closely packed. And in liquids, distances between atoms tend to fall somewhere in between. Cooling steam until it condenses into water, or freezing water until it becomes ice, decreases the space between its molecules.It’s impossible to completely remove all the space between atoms and molecules. To understand why, picture atoms and molecules as spherical balls. Packing balls into a box leaves empty gaps between them, and no amount of moving the balls around will get rid of those gaps. But natural forces such as heat or pressure can reduce the space between atoms and molecules that make up a particular substance, or change how they are arranged.I am a chemist studying the science of crystals. Scientists like me have found that we can mimic those forces in the lab – heating substances to extremely high temperature or squeezing them with a huge amount of pressure. In doing so, we rearrange their atoms and molecules to create materials with new features – sometimes by design and sometimes by surprise. How atoms or molecules are arranged in a substance has a lot of parallels to how flowers are arranged in a vase. Grace Cary/Moment via Getty Images Repacking atomsTo see how different a material can look and feel depending on how its atoms are packed, think about the element carbon, one of Earth’s most common elements and an important component of all living organisms. At room temperature and everyday air pressure, carbon exists as graphite – the material in pencils that people often call pencil lead. The carbon atoms in graphite form flat, six-sided – or hexagonal – sheets stacked loosely on top of each other. When you write, the force of your hand slides these layers apart, leaving a trail of black carbon on your paper.When squeezed with extreme pressure while it’s heated up, graphite transforms into a diamond. Scientists call this change a phase transition. The ingredients didn’t change – it’s still just carbon – but the pressure rearranges the atoms from flat sheets into three-dimensional shapes called tetrahedra. This arrangement keeps atoms from sliding away from each other and makes diamonds one of the hardest materials in the world. How much squeezing does it take? To turn graphite into diamond, you need a temperature of 1,832 degrees Fahrenheit (1,000 degrees Celsius) and massive pressure. Imagine the weight of 10 heavy elephants all balancing on the tiny point of a pin, right in the middle of hot lava. Rearranging the atoms or molecules in a substance can change it into something new. Mimicking nature in the labDeep inside the Earth, about 100 miles (161 kilometers) down, this process happens naturally but takes billions of years. Since the 1950s, scientists have learned how to recreate it in the lab to synthesize diamonds. They do this with the help of specialized equipment such as a multi-anvil press to provide the massive squeeze. In this device, extremely hard blocks fit together snugly like puzzle pieces around a sample. By squeezing the blocks together with the sample in the center, scientists apply an immense amount of pressure on it. They also heat the material with a laser or small furnace.Graphite treated in this way for several hours becomes a synthetic diamond. Other substances also transform. For example, companies that make cosmetics often use a substance called boron nitride because at room temperature and pressure it has a soft texture and the perfectly light touch of sparkle people love in makeup. Squeezing and heating boron nitride transforms the arrangement of its atoms from 2D hexagonal sheets into 3D cubic boron nitride. In this form, boron nitride becomes what scientists call a superhard material, second in hardness to diamond. People use it to make industrial tools such as drill bits and grinding wheels for heavy machinery.By forcing atoms together with pressure and heat, scientists can control how a material carries electricity, how magnetic it is, and how it handles heat. For example, a team of chemists working with iron atoms in a mineral called jarosite, found in the mountains of Utah and New Mexico, could control its magnetic properties by cooling or heating it to change the atom arrangement. Sometimes, scientists discover new materials by surprise, such as the 2025 discovery of the first gold-hydrogen compound. People have generally believed that gold doesn’t react with other elements, but it turns out that squeezing and heating a sample of gold caused it to form chemical bonds with hydrogen in the atmosphere. This discovery is so new that scientists are still learning about this material’s properties.Whether it happens naturally or in a high-tech lab, transforming the way atoms pack together can turn ordinary substances into extraordinary new materials.Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.Robin Macaluso receives funding from National Science Foundation.