TOR, the Target of Rapamycin was discovered a little over ten years ago in a genetic screen in S. cerevisiae in search of mutants resistant to the cytostatic effects of the antimycotic, rapamycin. Recent studies have placed TOR at the interface between nutrient sensing and the regulation of major anbolic and catabolic responses. The editors have gathered the leading figures in the field of TOR and its role in cellular homeostasis and human diseases.