Ubiquitin is a small protein that has a very big job. Or jobs, to be more accurate. Indeed, the ubiquitin system is central to--literally--just about everything significant that goes on inside cells, and to a lot of intercellular business as well. Once unknown and, until the 1980s, unheralded, the ubiquitin system is now one of the major areas of study in cell biology, biochemistry, and genetics, and the point of convergence for many disparate disciplines.