Size isn't everything

Much progress has been made recently towards uncovering the mechanisms that control the size to which organisms and their organs grow, and identifying some of the genes responsible. Size control, however, is only half of the equation. In growing to the right size, tissues must also grow to the right shape. A recent paper((1)) suggests that a hitherto overlooked cellular behaviour governs the size, and shape of a growing tissue, and issues a challenge to developmental biologists to identify the molecular mechanisms involved.