Although there are more than one great answers to this question here but I am surprised no one has pointed out the greatest theme (my opinion) of Professor Connes' work. He has reproduced the Standard Model of physics from purely mathematical work which is worthy of history books. He has given a fundamentally different direction to our quest for understanding the world. Essentially, (as per my understanding), he extends the geometrical picture of gravity given by Einstein to explain all of physics as geometry. Not only that, his geometrical world also has in-built time evolution. HisHe explains all this as starting from Heisenberg's matrix picture. Although many say Heisenberg's and Schrodinger's pictures are the same but H, he introduces the basic notion of non-commutativity with this matrix mechanics and uncertainty principle. He(Connes) gives a whole new calculus to perform differentiation and integration etc. I don't know why his work is not talktalked about more. [I
(I would love if someone could point out if I am wrong partially or completely because I am neither a mathematician nor a physicist.])