In the three decades prior to his death, Einstein's distrust of quantum theory isolated him from the mainstream developments in physics. All of his greatest contributions to science had been made by 1926, and from this point on, he remained a staunch opponent of the theory he had done so much to build in his earlier years. Einstein focused his efforts instead on developing a unified field theory, a theory which would explain both gravity and electromagnetism in one principled mathematical account. He hoped to resolve the conflict between the smooth continuum of space-time described by his general theory of relativity, and the jittery submicroscopic particle-world where quantum theory reigns. Although he never succeeded in this endeavor, in a sense he was simply ahead of his time: throughout the 1980s and 1990s, the primary goal of theoretical physicists has been the formulation of a grand theory of everything, or TOE, that would account for every element of physical reality.