Molecules were not "discovered" per se, but rather the concept and understanding of molecules developed gradually through scientific advancements. Here are a few key figures and contributions related to the development of molecular theory:

John Dalton (1803):

- Proposed Dalton's atomic theory, which introduced the idea that matter is made up of tiny, indivisible particles called atoms.

Amedeo Avogadro (1811):

- Avogadro's law stated that under the same conditions of temperature and pressure, equal volumes of gases contain an equal number of molecules.

Joseph Loschmidt (1865):

- Estimated the size of molecules and provided an early estimate of the number of molecules in a given volume.

Jean Perrin (1908):

- Conducted experiments that confirmed the existence of molecules and determined Avogadro's number, the number of particles in a mole of a substance.

Albert Einstein (1905):

- Provided theoretical explanations of Brownian motion, further supporting the existence of molecules.

The understanding of molecules emerged over time through the contributions of numerous scientists, and it continues to be refined and expanded through ongoing research in various scientific fields.