After completion of the human genome project, it was found that the number of genes involved (about 20.000 to 25.000) was much lower than expected to explain the observed biological complexity. This underlines the importance of proteins as the end products of genes in regulating biological systems.

Between the gene (DNA) level and the protein level there are several possibilities for biological modification that lead to a large variation in protein species. Proteins catalyze and regulate biological processes, and therefore, are keystones in the development of diseases. This makes them attractive targets for treatment with drugs and nutraceuticals and a focus for medical diagnostics (biomarkers).

New analytical techniques that were recently developed make it possible to systematically analyze in parallel numerous proteins in a cell or tissue expressed under a certain condition (proteome); this strategy is called proteomics. Proteomics is a very powerful and promising approach to study proteins involved in the development of disease.