In traditional slab-gel electrophoresis, the gel has two functions: it serves as an anticonvective medium, as well as a sieving matrix that provides separation. Because of the low convection, CE permits a gel-free separation at high voltages, and thus yields unprecedented resolution and speed. However, the situation is different for biopolymers such as RNA, dsDNA, ssDNA, or SDS-denatured proteins, which have a constant charge: size ratio. In this case, no separation occurs in free solution and some sort of sieving matrix still has to be used (however, the anticonvective property of the matrix is not needed any more).