The discovery of quantum mechanics and Einstein's theory of relativity, vital to much of modern technology and economic activity, including the transistor, the laser and the atomic bomb.

ECONOMIST: Letters

The Peking Man fossils are a vital component of the Out of Africa 1 migration theory, which proposes that Homo erectus first appeared in Africa around two million years ago before spreading north and east (modern humans, Homo sapiens, would follow much later and supplant all other Homo species).

BBC: 'Peking Man' older than thought

In traditional Chinese medical theory, the core concept is the qi, the vital energy that is believed to circulate throughout the body.

CNN: SPECIAL REPORT: HEALTH