Relativity is our viewpoint from an awkward position of the universe, while Quantum Mechanics is the other viewpoint. Both phenomena are like two sides of the same coin. Relativity is inside the light cone phenomena (since nothing can travel faster than light), while Quantum Mechanics is outside the light cone phenomena (allowing instant communications in ‘quantum entanglement’ experiments). Both are dictated just by the scale (i.e. whether we use classical/human scale or sub-atomic scale) for a very good reason (explained in detail in my paper).
But why does the transition from Relativity to Quantum Mechanics happens with decreasing size scale? That’s because, this is what is happens to spatial and temporal dimensions at different scales:
3+1 (Classical regime) <=> 2+2 (Compton regime) <=> 1+3 (Planck regime).
General Relativity makes things a bit tricky since it involves curvature/warping of spacetime, but it does not become incompatible with Quantum Mechanics. The only difference between the warped spacetime of General Relativity, and the flat spacetime of Special Relativity is very similar to the difference between a stretched rubber membrane, with and without a metal ball placed on it. This stretching also produces the same time dilation (as predicted by Einstein), but now it is due to the cos and sine components of the temporal dimension. General Relativity and Quantum Mechanics are the two pillars of modern Science. Reconciling the two leads us to 'Theory of Everything'.
The list of achievements in my above-mentioned paper is simply too long to be detailed here in this email. [e.g. ‘Principle of Least Action’ which comes closest to the ‘theory of Everything’ in physics, and from which, all known laws of physics can be derived, arises as a direct consequence of the better model of the universe as proposed in this paper]. My paper also explains why dualities like wave-particle duality, or Lagrangian-Hamiltonian duality arises. Duality is a bedrock concept of modern physics.
The crucial conservation laws of Physics arise from symmetries of nature (as per Noether’s theorem). We can directly see from this simple structure of our universe, why those symmetries (e.g. homogeneity and isotropy) arises in the first place.  
Nature, the ultimate judge, has stamped TOTALLY APPROVED on my paper.