Normally the target molecules of the electrophoretic process must be visualized in a staining process after the separation. Exceptions are coloured proteins, f.e. Hemoglobins or other dyes themselves used as tracking molecules. Prestaining (before electrophoresis): DNA-molecules can be tagged, DIGE is a prestaing method before Urea-IEF in a 2D-procedure. Prelabeling of proteins before SDS using T-Rex.