The mechanistic Target of Rapamycin (mTOR) coordinates eukaryotic cell growth and metabolism with environmental inputs including nutrients and growth factors. Extensive research over the past two decades has established a central role for mTOR in regulating many fundamental cell processes, from protein synthesis to autophagy, and deregulated mTOR signaling is implicated in the progression of cancer and diabetes, as well as the aging process. Many aspects of mTOR function and regulation have only recently been elucidated, and many more questions remain unanswered. In this review, we provide an overview of our current understanding of the mTOR pathway and its role in growth, metabolism, and disease. In order to grow and divide, cells must increase production of proteins, lipids, and nucleotides while also suppressing catabolic pathways such as autophagy. mTORC1 plays a central role in regulating all of these processes, and therefore controls the balance between anabolism and catabolism in response to environmental condition. The top open access journals are indexed in MEDLINE, PUBMED, SCOPUS, COPERNICUS, CAS, EBSCO and ISI.