Knowledge of cellular compartmentation is critical to an understanding of many aspects of biological function in plant cells but it remains an under-emphasised concept in the use of and investment in plant functional genomic tools. The emerging effort in plant subcellular proteomics is discussed, and the current datasets that are available for a series of organelles and cellular membranes isolated from a range of plant species are noted. The benefit of knowing subcellular location in determining the role of proteins of unknown function is considered alongside the challenges faced in this endeavour. These include clear problems in dealing with contamination during the isolation of subcellular compartments, the meaningful integration of these datasets once completed to assemble a jigsaw of the cellular proteome as a whole, and the use of the wider literature in supplementing this proteomic discovery effort.