No sooner had Einstein published his special theory of relativity in 1905 than the search for a generalization of this theory began. The search for a theory which, unlike the special theory of relativity, could deal satisfactorily with gravitational phenomena, and in which absolute motion of any kind and the existence of any preferential reference systems disappear completely. It was after ten years of hard, intense, and often frustrating work, that Einstein’s efforts were crowned with brilliant success in 1915, almost exactly one hundred years ago. The outcome was his General Theory of Relativity, “probably the greatest discovery ever made”. The lecture will be about Einstein’s life and work, mainly on the birth of general relativity.