"String Theory" is one of the most widely-known scientific theories to this day. It implies that the entire universe as we know it is made up of tiny, vibrating strings, similar to protons and quarks (although they move differently). String theory is the closest scientists have gotten to a quantum theory of gravity! Depending on the way the strings move (and if they're open or closed) different forms of matter are displayed. Each string has a vibrational "mode" that consists of special quantum numbers corresponding to a specific particle.

Michio Kaku, a theoretical physicist, is currently working to finish what Einstein had been working on in the past. He's building off of Einstein's theories of quantum mechanics, which in turn deals with string theory itself.