The is a long history about what makes up matter starting with Democritus in Ancient Greece and continuing through modern times. A critical experiment that spurred many future experiments was Rutherford's discovery of the nucleus in 1911. This experiment used a simple collision between Helium nuclei and gold foil and demonstrated the existence of the nucleus.

Prior to this experiment, the leading theory of what made up atoms is credited to J.J. Thomson. I Thomson suggested that matter was like a plum pudding where the