Discovery and understanding (1900-1927). Planck, Einstein, Bohr : experiments and early ideas ; Heisenberg, Dirac, Schrödinger : quantum mechanics and the quantum atom ; Application : six hundred million watts! -- Interpretation and mind-boggling implications (1916-2016). The essential features of quantum mechanics ; Clash of titans : what is real? Uncertainty, entanglement, John Bell, and many worlds ; What does it all mean? : quantum mechanics, mathematics, and the nature of science ; Applications : quantum computing, code cracking, teleportation, and encryption -- Our world of relativity and the quantum, from the Big Bang to the galaxies. Galaxies, black holes, gravity waves, matter, the forces of nature, the Higgs boson, dark matter, dark energy, and string theory -- The many-electron atom and the foundations of chemistry and materials science. Energy, momentum, and the spatial states of the electrons in the hydrogen atom ; Spin and magnetism ; Exclusion and the Periodic table ; The physics underlying the chemistry of the elements ; A few types of chemical bonds, for example ; The makeup of solid materials ; Insulators and electrical conduction in normal metals and semiconductors -- Quantum wonders in materials and devices, large and small. Superconductors I : definition, and applications in transportation, medicine, and computing ; Fusion for electrical power, and lasers also for defense ; Magnetism, magnets, magnetic materials, and their applications ; Graphene, nanotubes, and one "dream" application ; Semiconductors and electronic applications ; Superconductors II : large scale applications in science, power generation, and transmission -- Appendix A. The nature and spectrum of electromagnetic waves -- Appendix B. Empirical development of the Periodic Table of Elements -- Appendix C. Quantum computer development -- Appendix D. The atomic sizes and chemistries of the elements -- Appendix E. The production of X-rays.