John Dalton is the founder of atomic theory and one of the creators of modern chemistry. The teacher at a modest primary school in Manchester turned to ideas formulated a thousand years earlier by Democritus and other Greek philosophers, and proposed that the whole world consists of indivisible atoms and as a result of their interaction, elements appear, which in turn form chemical compounds. Although the existence of atoms was controversial until the beginning of the 20th century—that is, 100 years after the publication of Dalton’s work—it was the work of this educator, who did not receive a university education, that formed the basis of the conceptual revolution that changed the face of science.