Organ size determination and the limits of regulation.

The size of an organism dictates both its functional challenges and how it meets them. Despite being a universal feature of all living creatures, how an organism determines its size, and that of its internal organs, is largely unknown. In particular, the mechanisms by which organs sense magnitude and alter cellular behavior to ensure symmetry, proportionality and correct final size are unknown. This review outlines our current understanding of the field and highlights several important outstanding questions.