Unlike the genome, which is essentially identical in every somatic cell of an organism, the proteome varies across cells, and there is no self-replicating amplification mechanism for proteins like the polymerase chain reaction (PCR) for DNA. Because of this, methods that extract, separate, detect, and identify proteins from extremely small samples are needed.  In the current issue of Cold Spring Harbor Protocols, Duke University’s Erich Jarvis and colleagues provide such a method, Microproteomics: Quantitative Proteomic Profiling of Small Numbers of Laser-Captured Cells.  The protocol uses laser-capture microdissection to isolate pure cell populations from tissue sections and nanoscale liquid chromatography/tandem mass spectrometry to simultaneously identify and quantify hundreds of proteins from samples as small as 1000 cells. It is one of this month’s featured articles and is freely accessible here.