While ancient Greek philosophers like Democritus proposed the idea of atoms, Dalton was the first to put forward a comprehensive and scientific theory based on experimental evidence. His theory, published in 1808, included key postulates such as:

* All matter is made up of tiny, indivisible particles called atoms.

* Atoms of a given element are identical in mass and properties.

* Atoms cannot be created or destroyed.

* Atoms combine in whole-number ratios to form compounds.

Dalton's atomic theory revolutionized the understanding of matter and paved the way for the development of modern chemistry.