Body size is an intrinsic property of living organisms that is intimately linked to the developmental program to produce fit individuals with proper proportions. Final size is the result of both genetic determinants and sophisticated mechanisms adapting size to available resources. Even though organs grow according to autonomous programs, some coordination mechanisms ensure that the different body parts adjust their growth with the rest of the body. In Drosophila, Dilp8, a hormone of the Insulin/Relaxin family is a key player in this inter-organs coordination and is required together with its receptor Lgr3 to limit developmental variability. Recently, the transcriptional co-activator Yki (homologue of YAP/TAZ factors in mammals) was shown to regulate dilp8 expression and contribute to the coordination of organ growth in Drosophila.