 Modern chemistry is thoroughly atomistic. All substances are thought to be composed of small particles, or atoms, of the Periodic Table’s elements. Yet until the beginning of the 20th century, much debate surrounded the status of atoms and other microscopic constituents of matter. As with many other issues in philosophy of chemistry, the discussion of atomism begins with Aristotle, who attacked the coherence of the notion and disputed explanations supposedly built on the idea of indivisible constituents of matter capable only of change in respect of position and motion, but not intrinsic qualities. We will discuss Aristotle’s critiques of atomism and Boyle’s response as well as the development of atomism in the 19th and 20th centuries.