When and where did the first ideas about atoms appear?

For the first time in history, the ancient Indian and ancient Greek philosophers spoke about the atom, which is the smallest indivisible part of matter. And in the 17th and 18th centuries, scientists on the basis of experiments proved this assumption, which was based on evidence that not all substances undergo further decomposition into constituent elements.
In 1860, at the international congress of chemists in Germany, the concept of a molecule and an atom was adopted. Atom – is the smallest particle of chemical elements that make up a simple and complex substance.