Protein post‐translational modifications (PTMs) regulate nearly all biological processes in eukaryotic cells, and synthetic PTM protein tools are widely used to detect the activity of the related enzymes and identify the interacting proteins in cell lysates. Recently, the study of these enzymes and the interacting proteome has been accomplished in live cells using cell‐permeable PTM protein tools. In this concept, we will introduce cell penetrating techniques, the syntheses of cell‐permeable PTM protein tools, and offer some future perspective.