Could there possibly be a theory of everything?, well, its a little more than imagination, the history of physics suggests that such a theory may be possible. The theory of gravitation formulated by Isaac Newton provided a unified description of the motion of the moon and the fall of an apple. Similarly, the theory of electromagnetism formulated by James Clerk Maxwell unified electric, magnetic and optical phenomena. Also, Steven Weinberg and Abdus Salam independently formulated the electroweak theory, which unifies the weak interaction and the electromagnetic interaction by using a mathematical technique known as gauge symmetry.
Theory of Everything (TOE), is a theoretical framework that physicists believe if discovered, would provide a unified description of all the forces of nature. These forces, also known as interactions; are gravitation, electromagnetism, the strong force (a short-range force that holds atomic nuclei together), and the weak force (the force responsible for certain radioactive processes such as beta decay). To summarize fundamental physics briefly, a TOE would explain why the laws of physics are what they are.
Currently, the best candidate for a TOE is the theory of superstrings. In this theory, everything in the universe—all particles and forces and perhaps space-time itself—consists of fantastically small strings under immense tension, vibrating and spinning in a multi-dimensional superspace. Extra dimensions, in addition to width, depth, height, and time, are mathematically necessary to avoid tachyons (faster-than-light particles) and ghosts (particles produced with negative probability). These extra dimensions are thought to be compactified, or curled up into tiny circles, and thus rendered unobservable. Different elementary particles correspond to different quantized modes of oscillation of the string. Unfortunately, superstrings theory is very difficult to calculate with and has yet to yield testable predictions.