Unification was the theory that Einstein died trying to figure out. He wanted to create a law or mathematical equation that combines all the laws of the universe into one idea. Since Newton combined heaven and earth, Einstein wanted to combine everything else. The math of Quantum Mechanics and General Relativity don't coexist very nicely. This new theory would need to explain the four fundamental forces, but most importantly, it would need to combine the mathematics of all of them. This new theory called string theory may be the answer we have been looking for, but there are a few complications.
String theory is said to be the universe that combines science fiction with reality. It tries to describe gravity at the quantum level and it said to be vibrating strands of energy that vibrate in a multitude of different ways. They vibrate at different frequencies to create everything. It holds promises to answer complicated questions and is nicknamed "The Theory of Everything". Originally, there were 5 different versions of string theory, but it has been combined into 1 theory called the "M" Theory. Although, there are a few problems with this theory. If String Theory is correct, it suggests that there are 10 or 11 dimensions in our universe, instead of the 4 we know of. In addition, these strings of energy as so small (10^-35m) that it may never get any experimental evidence.