Book excerpt: This book presents the Eigen Theory of the physical world which consists of three stages. First stage formulates a pair of eigen velocity vectors, which produces the wave aspect of the wave-particle duality of matter. These vectors are functions of a pair of symmetric and antisymmetric tensors which are characteristic of gravitation and electromagnetism respectively. The second stage transforms the wave aspect of matter to the particle aspect which occupies a base manifold characterised by a second pair of symmetric and antisymmetric tensors. The third stage develops the particle aspect and its occupation of the base manifold the fundamental form of which is the Hydrogen atom. These three stages expose the reality behind matter-antimatter, wave-particle duality of matter, the results of the double-slit experiment, the nature of dark energy and the structure of dark matter. In Eigen Theory Quantum Mechanics becomes restructured, in particular the uncertainty principle ceases to exist, and General Relativity becomes complete.