Main building blocks of the material world consisting of an atomic nucleus (protons and neutrons) and an electronic sheath.

The greek philosophers Leukipp and Demokrit postulated that matter consists of small particles which cannot be further dissected. Physicists from the 19. century supported this concept experimentally. In the early 20. century, however, it was discovered that atoms are composed of smaller building blocks.

Further examinations of the electronic sheath of atoms layed the foundations for our understanding of the structures of molecules, the theoretical basis of chemistry. Further examination of the atomic nuclei (consisting of protons and neutrons) led to the understanding of radioactivity and to technical applications like nuclear fission or the use of isotopes.