Novel classes and applications of cell-penetrating peptides(CPPs) are being constantly discovered since they were first identified 2 decades ago. These short peptides either by covalent binding or by noncovalent binding can traverse cell membranes and deliver a variety of molecules that are unable to overcome the permeability barrier in their own capacity. As a nanoscale transport carrier, most of CPPs are non-toxic and have become a new potential tool in pharmacology, therapeutics, diagnostics, and studies...