The most important invention in the past two thousand years?
In my opinion it is the invention by Otto von Guericke in 1660 of a machine which produced static electricity. This device was the primitive tool which unlocked our understanding and application of electricity. Modern power generation, communication, computation, and almost all of our most important analytic devices stand on the foundation of von Guericke's machine. A long line of basic intellectual formulations from electromagnetism to the bioelectric properties of brain mechanisms owe a debt to this invention. When we discover how the human brain creates the covert models of its own inventions, the structure and dynamics of the brain's own electrical activity will undoubtedly be an essential aspect of the explanation.