This book presents Stein Theory, a genuine Theory of Everything: uniting particles, forces, constants, cosmology, and emergent phenomena under one geometric framework, complete with the relevant mathematics. All major constants and anomalies — including the electron magnetic moment, Lamb shift, proton structure, neutrino behaviour, gravity, dark matter, and cosmic expansion — are derived directly from the geometry of spinning two-dimensional units called steins. The result is a finite, unified model that eliminates infinities, resolves long-standing discrepancies, and opens clear pathways to new engineering frontiers.