Some years after Einstein published the General Theory of Relativity in 1916, he began to formulate an even more ambitious theory. Professional positions, first in Berlin and later in Princeton, gave him the latitude to work at his own pace. And after his wife Elsa died in 1936, Einstein's life increasingly centered on his work.
Einstein was driven by a vision. His goal was to describe all physical phenomena—from the smallest subatomic particles to the entire universe—under the umbrella of a "Grand Unified Theory." He never succeeded. But Einstein's dream did not die with him; the quest for the Grand Unified Theory is one of the hottest topics pursued in physics today. Einstein's work laid the foundation for much of the research into the evolution of the universe as well as modern technology, including lasers and computer chips. His enduring legacy will continue to inspire generations of great thinkers.
With the turn of the 20th century, the field of physics underwent two major transformations, roughly at the same time. The first was Einstein's General Theory of Relativity, which dealt with the universal realm of physics. The second was Quantum Theory, which proposed that energy exists as discrete packets—each called a "quantum."
Roughly half a century has passed since Einstein ceased his pursuit of one "theory of everything," but many physicists today continue the chase for a Grand Unified Theory in an attempt to understand the nature of matter, energy, space, and time.
Einstein the mortal—who capsized his sailboat, had a less-than-perfect family life, and had trouble getting his first job—quietly slipped away in a Princeton hospital. Einstein the legend will remain an icon of genius for generations to come.