Structural genomics aims to use high-throughput structure determination and computational analysis to provide three-dimensional models of every tractable protein. The process of choosing proteins for experimental structure characterization is known as target selection. In this nomenclature, the targets are regions of proteins to be studied by crystallography or NMR. Selection of the targets is principally a computational process of restricting candidate proteins to those that are tractable and of unknown structure, and prioritizing according to expected interest and accessibility.