String Theory....

When physicists started to combine the two titans of physics, meaning Quantum Mechanics and Relativity they encountered a huge problem. The two theories don't fit!. So they began a hunt for a new theory involving hyper-spaces and strings (and much much mathematics too) and that theory is string theory. It just basically says that everything (matter and energy) is composed of tiny vibrating strings which change structure when you pull them. It also says that there are "multi-verses" and our "universe" is just one of them.