The fundamental building blocks of all matter in the universe are atoms. They are incredibly small, with a diameter of about one ten-billionth of a meter, and are composed of even smaller particles called protons, neutrons, and electrons. Atoms are held together by electromagnetic forces, and the number of protons in an atom's nucleus determines which element it is. The interactions between atoms, governed by the laws of physics, give rise to the properties and behaviors of all substances, from the air we breathe to the rocks that make up the Earth. Understanding the structure and behavior of atoms is crucial for comprehending the fundamental nature of matter and the universe we inhabit.
