Cell growth is highly regulated and is controlled by the TOR signaling network. Dysfunction of signaling pathways controlling cell growth results in cells of altered sizes and in turn causes developmental errors and a wide range of pathological conditions. An understanding of the TOR signaling network may lead to novel drugs for the treatment of, for example, cancer, diabetes, inflammation, muscle atrophy, learning disabilities, depression, obesity and aging. There has been an explosion of knowledge in this area in recent years and this volume provides an in-depth review of our current knowledge of TOR complexes by the leaders in the field.