Over the past three decades the posttranslational phosphorylation of proteins, phosphoproteomics, has exponentially grown to dominate phosphate chemical biology. For the three canonical P-Ser, P-Thr, and P-Tyr residues, there are 520 human protein kinases in the kinomes and an estimated 250 000–270 000 phosphorylation sites in proteins, corresponding to 10–11 such sites in an average human protein. The introduction of the tetrahedral dianionic stable phosphate groups alters protein charge and geometry to mediate signal transduction in every phase of cell physiology. However, the focus of phosphoproteomics on the acid-stable canonical P-Ser, P-Thr, P-Tyr troika readily detectable as phosphopeptide fragments by mass spectrometry underestimates the prevalence of six other possible phosphoprotein types, including three phosphoramidate side chains (Lys, His, Arg), two acyl phosphate side chains (Asp, Glu), and the phosphorothioate side chain adducts of S-phosphocysteinyl proteins. A compendium of an expanded phosphoproteomics version 2.0 will probably include the full complement of nine different phosphorylated protein side chains.