Proteins separated by two-dimensional gel electrophoresis can be visualized by in-gel detection using -different staining methods. Ideally, the dye should bind non-covalently to the protein following a linear response curve. Since protein concentrations in biological systems may vary by six or more orders of magnitude (Corthals GL et al., Electrophoresis 21(6):1104-1115, 2000), the staining should allow for a detection of very low protein amounts. At the same time, saturation effects have to be avoided because they impede normalized quantification.Most proteomics laboratories apply Coomassie, silver, or fluorescent stains. Using the colloidal properties of Coomassie dyes, detection limits at the lower nanogram level can meanwhile be achieved. Characteristics like ease of use, low cost, and compatibility with downstream characterization methods such as mass spectrometry, therefore, make colloidal Coomassie staining well suited for the in-gel detection method in quantitative proteomics.