In single-celled life forms, the rate of cell growth and division is principally determined by the availability of nutrients. Multicellular organisms operate very differently, with cell growth and division also under the control of developmental programs that instruct cell behaviour according to a cell's position and orientation relative to others, and according to the mechanical forces that the cell experiences. In the fruit fly Drosophila, these three inputs have been shown to act via signalling pathways, transcription factors and microRNAs to regulate the rate of cell growth and division and can also act upon the mitotic spindle to control the orientation of cell division.