An adult animal consists of cells of vastly different size and activity, but the regulation of cell
size remains poorly understood. Recent studies uncovering some of the signaling pathways
important for size/growth control, together with the identification of diseases resulting from
aberrations in these pathways, have renewed interest in this field. This Review will discuss
our current understanding of how a cell sets its size, how it can adapt its size to a changing
environment, and how these processes are relevant to human disease.