The term ‘Proteomics’ was introduced in 1997 to describe a growing interest in the study of the proteome – the expressed protein set of an organism. As this new discipline evolved, it quickly became obvious that proteomics would be a very complex and ambitious undertaking, perhaps even more so than genomics, which had engendered it. New techniques for both the separation and analysis/identification of proteins were emerging or being refined, and these facilitated the development of this new field. Many proteomics experiments are now routine in some laboratories. In this chapter we describe a typical proteomics experiment, using examples from our laboratory: the separation of complex mixtures of proteins by 2-dimensional electrophoresis and subsequent identification of a protein spot by mass spectrometry with two commonly used instruments: MALDI-QqTOF and ESI-ion trap.