The Protein Microsequencing Facility was established in 2000 at the Scientific Institute San Raffaele-DIBIt, in collaboration with IFOM (FIRC Institute of Molecular Oncology), under the sponsorship of FIRC (Federazione Italiana Ricerca sul Cancro). The facility has the purpose to provide a protein micro-characterization service employing the most advanced technology. Access to mass spectrometry and bioinformatics is a crucial key in the emerging field of proteomics, the large scale study of proteins and of their interactions, which is giving a major contribution to the description and understanding of biological processes at the molecular level.