A Nature News article describes the initial plans for an ambitious effort to begin mapping the complete human proteome: the set of all human proteins expressed in all of our cells at all points during our development and adult life. This is a project of vastly greater magnitude and complexity than the sequencing of the human genome. Unlike the genome, which remains essentially static between cell types and over time, the proteome is tremendously dynamic, changing constantly in response to cell-cell signalling and environmental stimuli. via