Cold and pressure transform gas into liquid and then into solid. Van der Waals understood the phase diagram of liquefiable gas with the molecular volume and intermolecular attraction, however, was silent on how solid behaved1. Unfortunately, solid-state phase diagram have remained uncomprehended mystery; only its straight boundary2,3 was explained by struggle of order vs. chaos. Here we show that the volume of orbital overlap has its own energy, with the universal density 8.941 eV/Å3 announced as new fundamental atomic constant that determines the transition temperature TC. Furthermore, we devised solid-state tomography, valid to 5 TPa, - imaging orbital through the baric dependencies of TC. Triangle-shaped pattern of the diagram is explained by the only possible way, just as only one plane passes through triangle: -inflation of the intersection volume during the transition determines hysteresis, but its disappearance does triple point; -approaching ions, whose orbitals overlap, curves the line from zero-field-cooling (ZFC) TC to triple point; -the straight line between zero-field-heating (ZFH) TC and triple point is a consequence of straightening tilting angle. Diamond melting point, calculated from volumes of the tetrahedral covalent bonds, excellently agrees with real; furthermore, the points up to 2 TPa agree with experiment4. Our findings open up way to interpret antiferromagnetism and steric effect in mono, binary, and ternary transition-metal oxides and sulfides5-11, and advance in unravelling unconventional superconductivity12,13, ascertaining the roles of s- and p-hybridizations. Thereby, the importance of the solid-state tomography for organic conductors12,13 being high-compressible and interior of stars can scarcely be exaggerated.