“…The first and most common type is the removing or obtaining lattice solvent molecules in solids, which only involve the change of weak intermolecular interactions, − i.e., hydrogen bonds, etc., in the crystal. The second type is the reorganization of chemical bonds between existing compositions, in which there is no gain or loss of atoms in the crystal but only the bond-type isomerism or the formation or breakage of the bonds (i.e., coordination bonds of metal ions, or isomerism of the ligands). − The third type is the addition, elimination, and substitution reactions of ligands or metal ions, which involve the exchange of species and the breaking and generating of coordination bonds. − The last one is the chemical reactions on ligands, which is mainly the addition, elimination, replacement reactions on organic ligands. , The latter two types of SCSC transitions are more interesting due to changes in both composition and chemical bonding, which often involve changes in the structure and property. However, crystal transformations with changes of both covalent bonds of ligands and coordination bonds are relatively rare …”