Who established that everthing is made of atoms and developed the first major atomic theory of matter?

The concept that everything is made of atoms was established by the ancient Greek philosopher Democritus around the 5th century BCE. However, the first major atomic theory of matter was developed by John Dalton in the early 19th century. Dalton proposed that all matter is made up of indivisible atoms, each with its own unique weight and properties, and he laid the groundwork for modern chemistry through his systematic approach to atomic theory.