Chemistry is the scientific study of interaction of chemical substances that are constituted of atoms or the subatomic components that make up atoms: protons, electrons and neutrons. Atoms combine to produce molecules or crystals. Chemistry can be called "the central science" because it connects the other natural sciences, such as astronomy, physics, material science, biology, and geology.

The genesis of chemistry can be traced to certain practices, known as alchemy, which had been practiced for several millennia in various parts of the world, particularly the middle east.

The structure of objects we commonly use and the properties of the matter we commonly interact with, are a consequence of the properties of chemical substances and their interactions. For example, steel is harder than iron because its atoms are bound together in a more rigid crystalline lattice; wood burns or undergoes rapid oxidation because it can react spontaneously with oxygen in a chemical reaction above a certain temperature; sugar and salt dissolve in water because their molecular/ionic properties are such that dissolution is preferred under the ambient conditions.