Characterization of Hydrogen Bonding: From van der Waals Interactions to Covalency -- Intramolecular Hydrogen Bonds. Methodologies and Strategies for Their Strength Evaluation -- Changes of Electron Properties in the Formation of Hydrogen Bonds -- Weak to Strong Hydrogen Bonds -- The Nature of the C–H· · ·X Intermolecular Interactions in Molecular Crystals. A Theoretical Perspective -- Weak Hydrogen Bonds Involving Transition Elements -- Contribution of CH· · ·X Hydrogen Bonds to Biomolecular Structure -- Neutral Blue-Shifting and Blue-Shifted Hydrogen Bonds -- Hydrogen–Hydrogen Bonding: The Non-Electrostatic Limit of Closed-Shell Interaction Between Two Hydro -- Potential Energy Shape for the Proton Motion in Hydrogen Bonds Reflected in Infrared and NMR Spectra -- Molecular Geometry—Distant Consequences of H-Bonding -- Topology of X-Ray Charge Density of Hydrogen Bonds -- Structure–Property Relations for Hydrogen-Bonded Solids -- Unrevealing the Nature of Hydrogen Bonds: ?-Electron Delocalization Shapes H-Bond Features. Intramolecular and Intermolecular Resonance-Assisted Hydrogen Bonds.