Atomism is a philosophical theory that suggests that everything in the universe is made up of small, indivisible particles called atoms. This idea dates back to ancient Greek philosophers like Democritus and Leucippus, who proposed that these tiny particles combine in various ways to form all matter. Atomism laid the groundwork for modern scientific understanding of matter and its properties. In the 19th century, scientists like John Dalton expanded on atomism by introducing the concept of chemical elements as unique types of atoms. This development led to the formulation of the atomic theory, which explains how atoms interact through chemical reactions. Today, atomism remains a fundamental concept in both chemistry and physics.