I saw a documentary the other day where Michio Kaku said something that really peaked my interest. He said that Einstein in his last days was working on something having to do with how small geometries of some sort being the cause of gravity. Does anyone know the details of Einstein's Unified Field theory? What was his approach and reasoning? What was the physical model that he was using? Any help and insight into this topic would be greatly appreciated. I am fascinated by Einstein and his Unified Field Theory.