Two-dimensional electrophoresis (2-D) of proteins used to be an art practiced by a few researchers, and their worldwide meetings could be held in a side room of a medium-sized hotel. With the rapidly growing volume of sequence data produced by the genome projects and the development of new mass spectrometry methods, high-resolution protein analysis has become an important tool in molecular biology. High-resolution 2-D can reveal virtually all proteins present in a cell or tissue at any given time, including those with posttranslational modifications and rapid turnover rates. With the new analytical tools and the genomic and protein database networks, large-scale studies can be performed on the actual gene products or proteins, in their precursor, mature, and modified forms. This task has lately been called the proteome project. The proteome projects are the necessary complement to genome analysis, and aim to identify and characterize all proteins expressed by an organism or a tissue (1).