It has now been conclusively proved from various observations - and specifically by studying very distant type 1a supernovae - that we live in an accelerating Universe. The galaxies are receding from one another, not with deceleration as suggested by simple intuition as well as predicted by the original form of the General Theory of Relativity, but with an outward acceleration. Dark Energy is the presumed source of this acceleration and is known at present to constitute nearly 73% of the energy budget of the Universe. An introductory and semi-popular account will be given of the discovery, present status and implication of this phenomenon.